Assemble Tools and Materials and Build a Molding Mock-Up
Make a short length of mock-up molding to confirm the size/weight of the finished crown molding, and then purchase the stock baseboard, molding and other components. Assemble your tools and safety equipment. You will be working with power tools and creating saw dust, so be sure to wear safety glasses and a mask. The height of the ceilings will require standing on a ladder--using the right size ladder and bracing it for safety are standard operating procedures. Wear non-skid shoes that fit securely, preferably shoes that also have hard soles to save your feet from the distress of standing on the rungs of the ladder.

Locate and Mark Wall Studs and Ceiling Joists
Use an electronic stud finder to locate each wall stud and ceiling joist all the way around the perimeter of the ceiling/wall joint. Mark each with a light pencil line near the ceiling/wall joint where they will not be visible once you add the molding.

Re-mark the Pencil Lines with Painter's Tape
Re-mark the pencil lines with temporary pieces of masking tape/painter's tape set about 8 inches from the ceiling/wall joint. Once the tape is up, notice that the two sides of the ceiling that run parallel to the ceiling joists will offer only a thin strip of ceiling joist for securing the crown molding. The other two sides of the ceiling and the walls wear tape in regular increments all the way around. You will add the first piece of baseboard to the edge of the ceiling that offers only the thin strip of joist.

Adjust the Sliding Compound Miter Saw and Miter the Baseboards
Set the sliding compound miter saw to cut right-hand miters on the baseboards that will lie flat against the ceiling. Start with the blade in its center vertical position, then rotate it 45-degrees to the right. Cut four baseboards with the saw in this position. Then reposition the saw to cut left-hand miters on four additional baseboards, rotating it 45-degrees left of center. You now have eight boards with a miter on one end. Before you secure these baseboards to the ceiling, measure required lengths and cut the other ends for scarf joints where they will join each other in the middle of the walls to form one continuous baseboard.

Set the Saw to Bevel the Uncut Ends of the Baseboards for Scarf Joints
Set the sliding compound miter saw to "bevel" the uncut ends of the baseboards in preparation for scarf joints. Scarf cuts enable the baseboards to meet and overlap each other in a flat orientation with only a tiny visible seam. The bevel on the upper board overlaps the bevel on the lower board. Start with the sliding compound miter saw blade at a centered and vertical position and then tilt the blade at a 45-degree angle. Make the bevel cut on the four "upper" baseboards that will overlap, then tilt the blade at the opposite 45-degree angle to bevel the lower baseboards.

Add Construction Adhesive to the First Baseboard
Prepare to attach the first piece of baseboard that will lie flat against the ceiling and run parallel to the ceiling joists. Those two edges provide limited support for nailing the molding to the ceiling, so you will need construction adhesive to help secure them. Add a generous dollop of construction adhesive every six inches to the back of the first baseboard (and to any other baseboard set at the edge of the ceiling parallel to the joists).

Tilt the Baseboard and Rotate It Against the Ceiling to Avoid Smears
Tilt the baseboard slightly so that you press the un-routed/plain edge against the wall at the ceiling joint and the rotate it up against the ceiling. This method helps prevent the adhesive from smearing and being visible.

Use an Air Nailer to Secure the Baseboard to the Ceiling Joist Beside the Wall
Use an air nailer to drive nails through the baseboard into the edge of the joist immediately beside the wall. Drive nails every 12 inches along the length of the ceiling.

Drive in Pairs of Nails at Opposing Angles for a Mechanical Support
Drive pairs of nails at opposing angles on the interior edge of the baseboard to provide "mechanical" support for the trim until the adhesive dries. Use the air nailer.

Align the Mitered Baseboards at the Corner and Secure with Nails
Line up the opposing piece of mitered baseboard, matching the miters precisely at the corner. Drive two nails through the baseboard into each intersecting joist along its length. You now have one mitered corner made by joining two baseboards with respective right and left miter cuts. They end in the middle of their walls in 45-degree bevels for scarf joints.

Join the Ends of the Baseboards Mid-wall in Scarf Joints
Join the next piece of baseboard in a scarf joint, measured and angled properly with a 45-degree bevel in the correct orientation. Use the air gun to drive nails through the overlapping angles at the scarf joint and along the length of the board. Add the remaining baseboards against the ceiling, using miter or scarf joints as appropriate.

Work Around the Perimeter of the Room to Attach the Baseboards with the Same Processes
Work you way around the room, following the same process to attach vertical baseboards on the walls with miter or scarf joints.

Cut Triangular Glue Blocks to Support the Crown Molding and Add Nailing Surfaces
Cut many small right-angled triangular glue blocks to support the crown molding and provide an additional nailing surface.

Coat the Edges of the Blocks with Glue
Coat the two perpendicular edges with glue.

Press the Glue Blocks into Position Against the Baseboards
Position and press them against the baseboards at each marked stud.

Drive Nails into Both End of the Glue Block to Secure Them to the Baseboard
Drive nails into both sides with the air gun.

Install a Crown Stop Bracket on the Sliding Compound Miter Saw
Install a crown stop bracket on the sliding compound miter saw to hold the crown molding at the correct angle while the saw cuts correct angles for the joints.

Cut the Crown Molding into Appropriate Mitered Lengths
Cut the crown molding into the appropriate lengths with mitered ends for the corners or beveled ends for the scarf joints. Position it against the baseboard as appropriate for the type of joint.

Secure the Crown Molding tothe Glue Blocks with the Air Gun
Drive nails through the crown molding into each glue block with the air gun and along the top and bottom edge where it meets the baseboards.

Caulk the Joints in Preparation for Painting the Moldin
Run a bead of caulking over the joints in preparation for painting the molding. Other materials are more suitable if you plan to stain the molding.

Cover Nail Holes with Spackling
Cover the nail holes with spackling compound. Again, if you plan to stain the crown molding, use wood putty or other material that will accept the stain.

Paint the Crown Molding
Paint or stain the crown molding to match the rest of the d?cor.

Turn Off the Power to the Ceiling Fan at the Breaker Box and Remove the Trim Ring
Turn off the power to the ceiling fan at the circuit breaker and use a screwdriver to remove the trim ring where the fan meets the ceiling.

Detach the Wires and Mounting Bracket Screws and Lift Out the Fan
Detach the wires and bracket screws and lift out the fan.

Choose a Ceiling Medallion in the Desired Size and Design
Choose the ready-made ceiling medallion to go above the fan. These are generally made of lightweight molded plastic and come in a variety of sizes and designs. The large size of the room, the height of the ceilings, and large ceiling fan all suggest choosing a larger medallion.

Drill Pilot Holes in the Medallion for Mounting It to the Ceiling
Drill pilot holes through the medallion for mounting it to the ceiling. In this project, we drilled four pilot holes through the medallion at four equidistant locations along the curved edge--imagining it to be the face of a clock, drill at 12:00, 3:00, 6:00, and 9:00 o'clock.

Apply a Ribbon of Construction Adhesive to the Back of the Medallion
Apply a petal-shaped ribbon of construction adhesive around the center back side of the medallion.

Press the Medallion to the Ceiling and Secure It with Screws
Press the medallion to the ceiling, centered over the ceiling fan's mounting bracket, and secure the decoration to the ceiling with screws.

Install the Fan Over the Medallion
Install the fan over the medallion, reconnecting the electrical wires and reattaching the fan to the mounting bracket. We upgraded the fan to a larger and more formal model.