If you want to use glass I might suggest trying to get the tempered cutting boards. Glass is definitely the flatest material I have found so far. I epoxyed t-nuts ( _[=]_ )to the bottom of a tempered glass cutting board from Lowes and threaded round head carriage bolts ( C--- )into the t-nuts from the bottom. If you do this you'll get better results by using only three legs though as it only take 3 points to define a plane. Two legs on one side and the other in the middle of the opposite side. I am trying something different tonight. I am going to glue the head of a flat headed bolt to the board and then thread on very long (1.5" [//////////] ) nuts. I couldn't get quite enough adjustment with the t-nuts if the surface was very unlevel. I also bought a longer level (I had been using a 1" torpedo level) that is less affected by the small ripples in the textured glass.
Cutting board 9$
Longer level 4$
Nuts & Bolts 1$
Epoxy 3$
Time 1 Hr. including design and testing.
Phenochilus &TC4 Paul- I have heard and seen on some boards that the decals to not adhere well to the boards using the sticky backing. Guys at my track bought them and then they started peeling up. We figure its due to the chemicals we submit our boards to. At first I was just like "just use liquid nails to get it down, but we realized it would be impossible to get the decal entirely flat.
Just a thought.