I use small milk cartons to make gingerbread houses with my students. They must be rinsed and dried. I staple them shut again and glue them to an 8x11-inch piece of heavy cardboard.
I ask all the children to bring in one cup of powdered sugar and a cup of small candies, cereal, marshmallows, pretzels, etc. to share. I mix up the candies so the class has a good assortment from which to choose. I mix the powdered sugar with water until it's the consistency of thick glue. Graham crackers can either be hot glued or frosted to the sides and tops of the milk cartons to make the walls and the roofs. The children use the frosting and the candies to decorate their houses making them unique and beautiful. Frosting can be spread on the cardboard to make snow and pretzels can be used to make fences and gates.
Be prepared for cleanup by spreading newspaper over the tables ahead of time. This idea also works for older children using any shape of box for the base.