Always save boxes. Boxes simply used as they were meant to be used is enough reason to keep them, but they can be used for other things as well. Boxes can be used for storage containers. They can also be used to transport storage items.
Boxes can also be used as the main body of a box oven. The best video I have found for instruction in making a box oven is on YouTube: Gourmet Cooking in the Wild- Box Oven Chicken. This video not only shows how to construct the oven, but also shows how to cook a chicken in the oven.