In an effort to expand the knowledge here on Parkjets, we thought this video is a great instruction on how to bevel the edges of the control surfaces and hinge them on your foam parkjet.
The video is produced by the guys over at RCSuperPowers (who have great plans on their site) and is a great example on how easy it is to work with foam.
One note here is that Dave (in the video) uses a razor to simply cut away the excess foam, but it is very easy to use a bit of sandpaper and a block to simply create the necessary angle on the edge of the control surfaces. Either way, a very simple way to make sure your control surfaces have the necessary throw to make your parkjet do what you need it to do.