Pour one cup of cornstarch into the ziplock bag.
Measure out 1/2 cup of water.
Add four to six drops of food coloring (any color) into the water.
Pour a small portion of the water and food coloring mixture (about 1/2 or 1/4 of the bowl) into the ziplock bag with the cornstarch.
Knead the ziplock bag to thoroughly mix the water, food coloring, and cornstarch.
Add the rest of the water and food coloring into the ziplock bag.
Knead the ziplock bag until the ingredients are completely mixed. The most obvious sign of when it is finished is when there is no more corn starch in the corners. (pictured)
Pour the contents of the ziplock bag into a bowl to test the "oobleck."
Pick up the oobleck and see if you can roll it into a solid ball/clump.
Then, flatten your hand and see if the oobleck "relaxes" and turns into a liquid. If it does, then you have successfully created oobleck! (a substance that can be both a solid and a liquid.)