Prepare cake batter according to the directions on the box. You will divide the batter between one 8x8 square baking pan AND 6 muffin tins (greased). Bake for the recommended time and let cool for 10 minutes. Remove carefully from pans. Trim the top of the square cake so it will lay flat on your surface. Also trim the tops of 4 of the cupcakes to make them flat. Using some frosting as glue - place 4 cupcakes on the top of your square cake. Place the frosting container in the microwave for 10 seconds. Add food coloring and stir until completely combined and your color is even. The frosting should be soft enough to pour over your cake for an even coating. Pour slowly, starting with the four cupcakes and let the frosting drizzle of the entire cake. (You may want to place wax papers until the sides of your cake for easier clean up.) Now you should have a cute Lego cake!
You can also make a larger, rectangle cake using a 13x9 pan and all 6 cupcakes, but this takes more than one box of cake mix.