Aldi marble cutting board

[Johncs]

and granite. They say they can make to order, various materials. maybe if you said don't care what it looks like long as it's flat they might be able to do something for you ?

Ceramic tiles are hard and cheap. Has anyone checked them for flat?

[joe greiner]

As does all glass, if you use it upright.

Haven't tried sharpening in that position.

Cheers,
Joe