Not sure about marble...just thinking, eventually filling with dirt and more upkeep, not flat. I have mine on flat alum. sandwich panel for roofing about 6 inches thick,..got some for free, it's used in commercial buildings.

A sheet of pressure treated plywood works also, you can just lay it down, drive over with the mover to cut all the grass right up to. A pallet or bricks on top where the hive sits on, simple is better, don't go too high, making it harder for getting off heavy boxes for inspection and honey super. You need something easy to walk around, plywood is also nice to keep clean and lay down your boxes when working the hives, make sure the plywood slops a bit away from the hive.

Thanks Konrad, I will take note of your suggestions. How many feet do you think there should be between the edge of the plywood and the hive?

Guess it depends how much room you have or want to waste, I would think put two hives onto one sheet of plywood.