This instructable is about a solar oven I made out of an old picture frame, two cardboard boxes, some duct tape, aluminum foil, white glue and crumpled newspaper. You will need to find a picture frame. I used regular glass but tempered glass would be better as it gets very hot and could shatter if you spilled cold water on it. I think I used about a 12 x 14 frame, not sure as it was a few years ago. What ever size glass you find will decide the size of the inner box and the outter box should be 2-3 inches larger. You need to cut a hole in the larger box to fit the inside box then crumple up some newspaper and pack between them.
Next thing after the box is in the hole and newspaper is packed between them is to tape it up.