Cut out four circles from your Styrofoam using a foam cutter or long blade. Your circles should be in four different sizes: 10, 8, 6 and 4 inches in diameter.
Center your 8-inch circle on your 10-inch circle and attach it with hot glue or superglue. Center your 6-inch circle on top of that and glue. Affix the last circle to the top. Hot glue will dry quickly, whereas super glue may require a few hours to fully dry. To further secure your circles, consider poking toothpicks through the layers to help hold them in place.
Once the glue is dry, flip the hat upside down. Using a spoon, dig out a 1 inch deep hole for your head. You may want to measure your head so that it is an exact fit.
Paint your Styrofoam with red paint. Use high-gloss paint, or a simple acrylic or tempera paint. If you use acrylic or tempera, let it dry, then coat it with a thin layer of polyurethane for a shiny finish. Let your hat dry for 24 hours before you wear it.