Ideas for ceramic pots to do solar cooking.?

If you are using a gallon bell jar, why not just make some sort of tri-pod out of steel rod and try something simple like a hot dog to see if your experiment works. You could also use cast iron cookware if you could find a pan to fit in the jar.

I'm just not knowledgeable about making pottery so I don't know what to tell you to make. But, it's got to handle high heat.

I've played with cooking in a solar oven. It was a pain because I had to adjust the oven every few minutes. (Turn it a bit to face the sun). I used pyrex bakeware.

I baked a macaroni and cheese casserole and some chicken enchiladas.