Work down the side and into box. Make sure that your foil lays flat and you do not puncture the foil. Mold the foil into the side and corner seams as you go. Continue wrapping until you have reached the edge of the foil. Overlap foil edge by about 1 inch and tape.
Some people only foil the inside of the box.
Start your next piece of foil by overlapping the first piece by 2 inches or more based on the size foil being used. Repeat until the width of the box is completely covered. Repeat this step running the foil the length of the box, making sure every exposed piece of cardboard is covered. If there is any cardboard exposed on the inside of the oven, it will burn. Do not use any tape on the inside of the box.