To make a simple and cheap solar cooker that can be folded and stored you will need:
A piece of cardboard (not to thick so it can be folded) 122 cm long and 91 cm wide
Aluminium foil (enough to cover the surface of a cardboard)
Glue (I used white glue for wood and it worked well)
Measuring tape or a ruler
Step 1: Plan
This is how you should cut your piece of cardboard. Broken line represents where the cardboard should be folded (not cut). The holes for assembling (2 narrow rectangles on the lower part) should be made at the end so you can find out the exact position for them.
Step 2: Glue the Foil
Cover all the surface with the shiny side of aluminium foil.
Step 3: Preparing for Cooking and Storage
Put the ends of the upper part in the holes on the bottom when you want to cook something. When not in use fold the cooker and secure it with a rubber gum. This is the greatest advantage of this type of solar cooker.
Step 4: Some Tips About Cooking
Use a small cooking pot, preferably black and put it in a heat resistant plastic bag. Use several stones as a pot stand. Place it on the cooker and orient it at the sun. I hope to post a video of cooking something soon when the weather gets better.