Miniature stone oven?

Hi, I want to build a small stone oven myself. I want to make the stones myself using my own formwork and mortar them with fireproof mortar. Is air-drying clay suitable for making stones? I think I can form good stones, but I'm not sure if they'll be heat-resistant, since I want to build a stone oven with a fire. Do you have any other ideas for materials I could use to cast or shape these stones, or will it work with air-drying clay or modeling clay?

Thanks