1. Before you start, be sure there is no sign of dirt or broken eggs on the carton. If you use a plastic foam carton, first wash it in soapy water. For a paper carton, place it in a microwave oven on high for 15 seconds.
2. With an adult's help, cut the carton into the shapes shown in photo, above, or create shapes of your own. Holding the mask away from your face, cut holes for the eyes. Make sure the holes are big enough to see through.
3. Use paints or markers to add designs to the mask. Let it dry.
4. Punch holes at the sides. Insert a shoelace or ribbon into each hole, knotting at the end to secure. Tie the ribbons or laces together to fasten the mask.