Being a retired instructor I have built many of them, best design uses wood. We call them toilet seats. I use two different sizes, one about 16” square and the other about 24” square. The bases are made using 4x4 stock and the tops are 3/4-1” plywood. The reason I use 4x4 stock for the base, it gives me a good solid stand to mount and run an engine on and because it is over engineered it doesn’t move around much. After you have nailed or screwed the five parts together, drill or cut a three inch hole in the top, to stick the crankshaft through. You will have to drill 1/2” mounting holes the first time you use it. When not in use it only takes up 5” of space when tipped on its side. Just another option.
