How do you make oobleck?

To make oobleck, you'll need just a few simple ingredients: water, corn starch, and food coloring. In a large bowl, add a few drops of food coloring to a cup of water. Slowly stir in a cup and a half to two cups of corn starch until the mixture forms a gooey slime.

Can you make oobleck with flour?

Flour (standard wheat flour) will not make Oobleck. Once combined with water, it will create a paste instead, which is how a simple homemade glue is actually made. The usual ingredient is cornflour but you can also use arrowroot powder or tapioca powder instead, see: How to Make Oobleck without Cornstarch.