In a small bowl add hot water and borax power. Stir until you dissolve the borax(or almost).

In a separate small bowl, add glue and paint and mix well.

Add cornstarch to the borax water and mix well. Pour in the glue to the cornstarch mixture. You will see the glue mixture become a hard glob and not mix well with the borax water.

Knead the glob with your fingers, while in the water, removing any bubbles and mixing thoroughly.

Remove from the water and knead in your hands.

Divide the material in half and shape it into a ball by rolling into your hands. Continue to roll and shape for a significant amount of time, I'd say at least 20-30 minutes. The longer the better. Bounce the ball and reshape if necessary.

Store in an airtight container or your ball will dry and crack.