Line a large jelly roll pan or broiler pan with foil. Grease the foil.

Put the turkey on a surface, breast side down.

Find the wishbone and cut around the bone. This is to make carving easier.

With sharp kitchen shears or a sharp knife, carefully cut down each side of the backbone; remove the backbone. You can freeze the backbone and use it to make a stock. 

Rinse the turkey and remove any bone fragments and excess fat pieces, etc.. Pat dry.

Place the turkey on a slip-free surface, breast side up. Press down on one side of the breast, close to the breast bone, until you hear a crack. Repeat on the other side of the breast. Use a clean towel to keep your hand from slipping. 

Transfer the flattened turkey to the prepared pan.

Turn the thighs outward, as in the picture, and tuck the wing tips under the bird. 

Heat the oven to 450 F. Rub the oil all over the turkey, sprinkle with salt and pepper, and let it stand at room temperature for 20 minutes.

Roast for 1 hour and 15 minutes, or until the thickest part of the thigh reaches 165 F on an instant-read thermometer or oven probe. Let the turkey stand for 20 minutes.