I have built and been using the CooKit solar cooker design and it works well.
(see link below)
I have found that a cast iron skillet works well with a glass lid. Most of the
time I do not use a oven plastic cooking bag around the skillet unless sun
is not strong enough. It is best to keep the cooking pan not to deep.
The PDF below will also give some ideas about how to cook different things
and the time it takes. It has plans for the CooKit design and can be built
easily with glue, aluminum foil, cardboard, cutting tool. Costs less than $7 to build.
Here is a link to a PDF file:
http://solarcooking.org/plans/Plans.pdf