LOL, I went through a few years of trial and error, and I still sometimes see things that are so easy and I just hadn't thought of them. Depending on the material and the number I am working on, I start the angles on the disc sander table or the band saw, just to get them approximately right, and then finish by hand on the belt. I don't really care whether they are exactly 45* as long as they are all reasonably symmetrical.
Stefan