One of the secrets to getting a strong glue joint is to spread the glue evenly before joining the surfaces. A great tool to do this with is hidden where you may never think to look...right inside an ordinary foam brush.
If you peel away the foam on the outside, what you'll find inside is the perfect plastic glue spreader.
If you've got larger surfaces, just choose a larger brush. Inside, you'll find a larger glue spreader.