Add 1 tablespoon of contact lens solution and stir with a spoon. If the mixture is still very runny, slowly add a bit more contact lens solution, mixing well and stopping as soon as the mixture can be peeled off the sides of the bowl.
Break off a piece of Model Magic and knead it into the glue mixture. Slowly add the remainder of the clay, kneading it all in with your hands. It will start out very sticky, but the more you knead it, the less sticky it will feel.
Once the slime is no longer sticky and you are satisfied with the texture, the slime is ready for your child to play with!
Video
Notes
Make sure the contact lens solution you use lists “boric acid” and “sodium borate” as ingredients. If those ingredients are not listed, the slime will not form and the recipe will not work.