Pour 4 oz white school glue into a bowl
Add 4 oz water and mix well
Add food coloring if desired and stir
In a separate cup, mix 1 tsp borax with 1 cup warm water until dissolved
Slowly add the borax solution to the glue mixture a little at a time
Stir until the slime starts to form
Knead the slime with your hands until it is no longer sticky
Add a small amount more borax solution if needed
Store the slime in an airtight container