I only found one website that has instructions, and those aren't very good, but get ahold of a girlscout and ask about the "winebox oven." Find a good cardboard wine box (that holds bottled wine, not the box of wine with the mylar bag inside)as the cardboard is heavier duty. Line the interior with aluminum foil, holes half way up from the bottom on the sides to suspend a grill. A small tin can placed in the bottom with charcoal briquettes. the open side has to still have the cardboard attached as the "door." There is enough space around the "door" to let air in for the charcoal. If I remember, four briquettes equals 350 degrees. Each briquette added to that adds 50 more degrees. I have had bread and brownies baked inside one of these. I would imagine you could bake potatoes, fish, chicken, etc. I don't know about heavy pieces of meat like steaks or pork chunks. I suppose any heavy duty cardboard box would work, but I think the size of the wine box is part of the cooking/temperature equation.

A Girl Scout camp I worked at many years ago had some of these that had held together for years. They weren't used too often, but could be folded up and stored easily when camping season was over. Not so much for back packing but they can be used for car camping, vehicle bug out rigs, or at home without power. I think grills could be found easily, or improvised with coat hangers or similar.

This is my initial newbie post. Hope it is informative and I didn't break any rules.