Mix together the sugar, cornstarch, and water. Heat, stirring often until thick. Let cool then divide and put in ziploc bag. Fill to the one cup mark with soap flakes. Mix until you have a thick paste.
Press spoonfuls of soap into the ice cube tray.
You can repeat this with several different colors. Elmer's glue and liquid starch. Mix equal parts of Elmer's glue and liquid starch and knead. Don't give up-you may have to add more glue and knead some more. If it is sticky add more liquid starch.