I bought a new miter saw and immediately started making a stand with it. Sort of an M.C. Escher kind of thing went on. I looked at a whole lot of examples on here and other places, and pulled them all together to make my own design.
I have some 32" wings fold out with some door hinges. The genius part (I know I'm too humble) is how I secured the brace pieces. I cut the brace at 45* angles and then screwed down other pieces with 45* angles to hold everything together. I screwed little wooden pieces on either side to hold the brace in, except on the stand part where I left one side open to remove it. (Check the pictures cause that was as confusing as all get-out)
Anyway as far as dimensions use the saw itself to judge, but my top shelf is 16" x 20" and everything is set at 34 1/4" high because that's the height of my table saw, so now the wings can by an outfeed table or side support with some finnagling.