Close the lid of the pizza box. Fold back the flap and prop it open with a ruler or stick. Place the box outside, with the flap facing the sun. The sun should reflect off the flap and into the box. Let the food cook until it's done, which may take 30 minutes to an hour. If you'd lke, you can place a thermometer inside the box and measure the temperature every 10 minutes to see how hot it gets. Enjoy your snack when it's ready!
Safety note: The solar oven can get very hot. Use caution when handling.