I made my first solar oven from a silver windshield shade. I found the idea on the internet. I formed the windshield shade into a funnel shape, set it on a box and put it out in the backyard. I placed a rack across the box to set the pot on. The pot is enclosed in an oven cooking bag.
The first meal was just hot dogs cut into pieces in some canned chili. I had no other instructions and didn’t know how long to let it “cook” or at least in this case, “heat up”. I ended up taking it off just a little too soon and the hot dogs were not fully heated in the center. But it was warm enough! And we were hooked.