You will need:
Basic white school glue
Borax (found on laundry aisle)
To make, mix equal parts of glue and water in a bowl. Set aside. Pour one cup of water in a bowl and add about one tablespoon of Borax and mix.
You want the Borax to completely dissolve in the water so that the water is saturated. Ours didn’t completely dissolve so we added a little bit more water until we got it just right. Once the solution is saturated, add two tablespoons of the glue and water mixture and stir quickly. The Borax binds the glue molecules to each other making the whole mixture a thick slime.
Add food coloring and knead into slime until color is thoroughly mixed throughout the slime.
You can make multiple batches of different colors and store them in Ziploc bags to keep them from drying out.