Lynda has experimented with pizza box cookers.
Free is making a panel cooker from a car sunshade. (And has other plans too.)
Solar Cookers International are currently promoting the 'Fun-Panel solar cooker', which they say you can make in under an hour - with a single cardboard box, some foil, tape, string and glue. (Plus an oven bag.) The box cooker we made this year was pretty simple - but this is simpler! I'm keen to try it.
You generally need to solar cook in a thin, dark pot that will absorb the heat. However, thin dark pots that are the right size for your cooker are not always easy to find. In the book Cooking with Sunshine, the authors give several ideas for improvising:
* You can paint the outside of a pot black.
* You can drape a black cloth over your pot.
* You can even cook baked potatoes or corn in old black socks!