Box ovens are amazing! They do a great job at baking foods outdoors. Using a box oven is a great way to make cooking with charcoal much more efficient. The box oven keeps heat contained inside the box instead of allowing heat to escape from the coals into the air. And the best thing about a box oven is that you can make one yourself!
Place a sheet of heavy-duty foil (make sure the sheet is longer than your box), shiny side up, on level ground or use a baking sheet. Space soda cans on the foil/baking sheet to support the cooling rack. Position the cooling rack so that only the very corners are resting on the soda cans. Check to make sure the cans aren't spaced too far apart to prevent the box from fitting over them. You can regulate the temperature of your oven by the number of briquettes you put in it. One briquette equals approximately 35 degrees F(ie. for 350 degrees, use 10 charcoals). Using tongs, place hot briquettes on foil, spreading them out evenly between the cans and along the edges. Don't pile all of the briquettes in the center because your food will burn. Place them around the edges exactly where the red arrows are pointing at in the image below.
To preheat the oven, place the apple box over the hot coals and empty rack and let it stand for 5 minutes. The charcoal will become whiter as the heat spreads. Once preheated, carefully lift the apple box straight up off the coals and rack, taking care not to tilt it, and place it beside the ground foil, face down. This holds trapped heat in the box. Quickly place your food on the cooling rack that on top of the soda cans and replace the box over the coals.
The charcoal will burn for about 35-40 minutes. When longer cooking times are required, you can add more hot charcoals by slightly lifting the box and slipping them in with long tongs. We found that if a recipe calls for 45 minute baking time and it is warm outside, no additional charcoals are necessary. Remember, one briquette equals approximately 35 degrees F (350 degrees=10 charcoals).