I am going to build a couple of cajon's for my sons for Christmas. These are basically a plywood box with 6 sides with a hole for sound that is used as a drum. If one does a google image search for "cajon drum" you will see many fine examples. But they all appear to have nice sort of rounded corners and edges. They are made in some variation of plywood generally 1/2 and 1/4 inch. Does anybody have some good tips on how best to get this look when joining plywood? I will be using Birch, probably 1/2 in for the sides, top and bottom, 1/4 inch for the front and back.