Paper or newspaper
Step 1: Find the Right Size Boxes
To find the right size boxes you need a box a bit bigger than what you are going to cook. Then you need a box slightly bigger, than the other box, in every dimension.
Step 2: Apply the Foil
Use the foil to cover the inside of both boxes.
Step 3: Put in Paper/Newspaper
Put the paper or newspaper on the bottom of the larger box, and put the smaller box in the bigger box. After that, put some more paper/newspaper between the boxes.
Step 4: Attach the Tabs
Take the tabs of the inner box and attach them to the outer edges. Cut off the excess tab.
Step 5: Create the Cover
Take the sheet of cardboard and cut it to fit the top of the outer box. Cut three of the four sides of a square, with a small margin, on the inside, and lift it up.
Step 6: Put Some More Stuff on It
Add foil to the flap and plastic wrap to the hole left from the flap. Use a strip of cardboard to prop up the flap.
Step 7: Add the Cover to the Larger Box
Attach the uncut side of the covet to the back end of the box to make a door on the top, for accessing the inside.
Step 8: Put the Box in the Sun
Align the side opposite of the hinged side toward the sun, and wait.