Jeremy Osner
The flat surfaces I'm using:
* A 9"x18"x3/8" piece of glass which I bought recently; I sprayed glue on it pretty heavily to mount the sandpaper. I will take the sandpaper off and clean it up, and then use water or repositional adhesive.
* a 12"x12"x1/4" piece of granite which I bought many years ago, and found yesterday in the course of the big shop cleanup underway. It has sandpaper glued to it from years ago. Thinking I should probably soak in solvent to clean it up and then check if it is actually flat, I don't know if it is.