It's so simple to make, and there are only 3 ingredients:
1 Cup Water
2 Cups Cornstarch
Place a few drops of food coloring into the water (too much and your hands will likely stain when playing--and believe me this one isn't just for the kids, you'll want to check it out) before slowly pouring it into the cornstarch and mixing once more.
It will become tough to mix, but don't give into the urge to add more water to make it easier. That's it now play away!!
At first our mixture seemed slightly watery, but she played with it long enough that it gradually thickened over time. This entertained my daughter for hours!
And YES you can stick your toes in!