In a 2 or 4-cup glass measuring cup, combine one cup of boiling water and the first gelatin powder. Stir constantly until dissolved. Add enough ice to bring the water level up to two cups and stir until ice is completely dissolved. Divide gelatin evenly among the 12 jars. Can use a canning funnel to make this less messy.
5 3-ounce boxes different flavored jello
Place jars in the original divider box they were purchased in (if you still have it) and put them in the refrigerator for about 30 minutes. Repeat until all five colors are used and jars are full. Great summer fun for the kids!