I built my first solar oven in the summer of 2006. I followed the minimum box cooker plans at www.solarcooking.org. It has seen a lot of use and is getting a bit tattered. I’ll have to remodel it one of these days.
My second oven is a slightly smaller one made from an LCD monitor box. The walls are made of several layers of cardboard and it has a Plexiglas top. The result is a very sturdy oven that should last a long time. This oven is well insulated and retains heat much better than my other two ovens. It still has the original plastic handle which makes it somewhat portable as well.
My most recent project is a panel style oven built using the plans for the Kundaper variation of the CooKit. It is really just a piece of cardboard with layer of aluminum foil, cut and folded to direct the sunlight to the cooking vessel. An oven bag encloses the cooking vessel to create a “greenhouse” effect.