My husband is actually making one for me as we speak. I have a little round plastic Wilton one. But it's too small for the square cakes that I'm making. So we went to Lowe's and bought some wood, a lazy susan, a piece of stone, some screws, and some grout stuff to hold the wood to the stone.
So from the bottom up it will be a piece of wood, lazy susan, piece of wood, grout, stone. It cost about $35. And it's going to be an 18x18 square.
I was just going to order one from Global Sugar because they have some really good ones that you can flip over (rectangle on one side and round on the other side). But it was going to take too long to get it.
I'll let ya know how it turns out!