ORIGINAL: gus
Surprised that no-one has mentioned the use of thick glass. Much cheaper than granite, more available, and at least as strong.
I have a 2x4 sheet of tempered 1/2inch glass. Pretty darn flat.
gus
Gus - I build on 1/2 glass, but it will bow significantly if it's not supported. I used a long level to make sure it's flat by putting shims between the glass and the frame where needed. It was a pain and tedious and after a month I had to do it again, but it's pretty darn flat now.
