In my buying trips to gem and mineral shows I often run into items carved from interesting rocks. Once in a while these can be used in a table top. I found this plate cut and polished from a slab of fossiliferous Moroccan stone. I bought it becase the plate was much flatter than others I had seen.
In this case I used a rusted whiskey barrel hoop for a rim, steel hairpin legs, and included slabs of local sandstone. I made the table below for a person who wanted something other than hairpin legs for the table base, but with a flat plate carved from Moroccan fossiliferous stone.
I have several more flat Morrocan stone pieces that I could use in a table for you.