Attach two temporary two-by-fours at the upper edge of the vanity, setting them flush with the vanity’s upper horizontal surface and placing the screw holes as inconspicuously as possible. The two-by-fours will extend the bottom of the concrete form so that the countertop will have a decorative lip or overhang on completion. We wanted the overhang on the two exposed edges of the countertop only—so we taped (with electrician’s tape) the two edges that butt against the walls to seal the bottom of the form and protect the walls.
