Here are the ingredients:
Water and cornstarch, a bowl or plastic tub (or a kiddie pool if you like). That's it!
How do you make it, you ask. Very easily:
Put some cornstarch in the bowl. Slowly add water. As you pour, stir (with your free hand). The trick is to add just enough water so that you can roll the mixture into a ball, stop rolling and it melts between your fingers.
Now have some fun!