"The Toddler Busy Book", by Trish Kuffner page 356
Homemade Modeling Clay
2 cups salt
2/3 cups water
1 cup cornstarch
1/2 cup cold water
Stir salt and water in a saucepan over heat 4-5 minutes.
Remove from heat; add cornstarch and cold water. Stir until smooth; return to heat and cook until thick. Allow the clay to cool, then shape as desired. When dry, decorate with paint, markers, glitter, and so on. If you like, finish with clear acrylic spray or clear nail polish. Store unused clay in a Ziploc bag.
I used kosher salt and I think I should have used table salt, but oh well. I'm waiting for it to cool but so far its super sticky, I'm hoping for it to be a little more smooth, I think the kosher salt is the problem.