Stir hot water into the soap flakes.
Spoon some of the mixture into an old margarine container and add a few drops of food coloring until it's the color you like.
Fill ice cube tray with soap and put in a warm breezy place to dry -- takes 48 hours to one week.
Take out of mold and let dry for another week before using.
Use crayons to draw on the side of the bathtub during bathtime.