The first time I heard about this, I didn't believe it! I had to try it in the back yard, and soon my whole neighborhood smelled like fresh-baked chocolate chip cookies. This is the ideal cooking method for someone who'd like to cook meals outdoors a little beyond the usual hot dogs ona stick, but doesn't want to invest much money or take a lot of trouble.
Essentially, you're trapping heat from charcoal briquettes inside an insulated cardboard box, placing the food in the box along with the briquettes. (Note: since the briquettes are in the same container as the food, I recommend against the use of any of the self-starting charcoals -- your food could smell of charcoal lighter fluid!)
How do I make one of these? The oven shown above is the simplest possible style -- take a sturdy cardboard box (larger than your baking pan!), line it with heavy-duty aluminum foil, and tape the foil to the outside of the box with duct tape. (Don't use any tape or glue on the inside of the box -- again, the fumes will be in with your food!) The box shown is on the ground in a fire ring, with one or two corners lifted slightly off the ground to allow a small amount of air inside by using a friendly rock or two under the corner.
This picture shows what goes inside the simple oven. We were cooking "Individual Mini-Pizzas", using split English muffins, spaghetti sauce, and pre-grated cheese. These are done when the cheese is melted. (We could have used pepperoni, onions, or bell peppers -- but anyone who wants anchovies gets her own box!) A sheet of heavy-duty aluminum foil is placed on the ground (forming the bottom of the box), four soda/soup cans are used to lift a small grate off the ground, and the baking pan is placed on the cans. The cans are more stable if filled with water or sand!
The temperature can be estimated by allowing 35 degrees F per briquette (works reasonably well in the range of normal baking temperatures). Spread the briquettes on the foil, carefully place the box over the food, and bake just the way you would at home.
Other easy things you could bake? Apple crisp, brownies, cinnamon rolls, coffee cake, muffins...
This oven was put together by a Girl Scout troop many years ago, and opens from the side (the door is rotated up and lying on top of the oven in this picture). The door is part of the oven. The charcoal is placed in a small disposable baking tray and slid into the oven. Over the years, many layers of foil were placed on the baking tray and the bottom of the oven. Temperature control is about the same as in the simple oven above.
This shows the same oven closed -- at this point, the door doesn't close very tightly, and must be held shut with a rock.Other still more elaborate ovens can be made -- at the time this one was built, one with a piece of oven bag in the top as a window was made, but that one didn't hold its heat nearly as well (would've worked better with the oven bag on the back instead of the top).
I don't have recipes here, because anything which can be baked in an oven at home can be baked in a box oven. You'll have to watch the charcoal, if the cooking time is long, adding more as required.