I made mine out of a bucket, a windshield reflector, a cake cooling rack, a black pan and a glass lid. Put a frozen casserole in it and it was boiling in 90 minutes. I think I have a picture somewhere. It all folds down and is completely portable. I have also seen them made with two reflectors, one vertical and one horizontal across the seat of a white resin garden chair.
Yeah, here's the picture:
I later made a prop out of a cardboard tube from wrapping paper, with non skid shelf lining over the ends, to open up the angle a bit more and get more sun. When I want to use a larger container, I use a large cookie rack and flatten out the tip of the cone a bit more. I also have a circle of glass that I can put on top of a large black pot. This reflector is the extra large, double reflective kind for a truck or SUV.
I made a solar oven last year that looks a lot like the sun oven from earlier posts. This spring I re-made the reflector panels, covering them with reflective mylar instead of the aluminum foil I had last year. I roasted myself a chicken in it today and them baked myself a cake. It was a good day, especially since it's my birthday.
Man, am I late in the game. Well I made one, but I can't really say how well it worked, because everytime it got to a good temp and started heating things up, the wind would blow the top off. I did it with cardboard, which I spray painted black and topped with an oven roasting bag. It was insulated with 4 inch insulation, which was covered with foil...also painted black. It had a thermometer for a BBQ pit to register the temp.
In theory, it should have worked, but if I try again, I will use treated wood and make it big and have it on a stand with wheels.
I have built 5 solar ovens and I use two personally almost every day. Mine is made with 1/2 plywood, duct board, masonite board, glass and mylar. I can make everything that you could possibly want. BBQ ribs just fall off the bone, cherry pie, sourdough bread. You name it, I can cook it and my family loves it. The temp is a consistant 350 - 375 degrees on a sunny day. One thing that I really like is that I can put my food in the oven around 8a.m., aim it toward the mid-day sun and when I get home around 4pm everything is juicy and delicious! Yum! wouldn't trade my solar oven for the world!BTW the ovens cost around $50 - $75 depending on prices in your area.