What’s the base made out of? I’ve been thinking about making a base in my ceramics shop to be able to make a pyramid on top of out of used balls?

Would love to see what has been made before. I also wonder if it has a lip. With a divet for the first layer of balls a side would not necessarily be needed. Or with sides divets wouldn’t be neeeded. I’m still debating what would work best with what I’m making.

Awesome thanks