Question: How do I keep my homemade slime from getting hard?
Option 0: You will want to keep it stored in a tight plastic container with a lid or Zip-loc bag. Also, you can gently lay it on a toaster oven tray for 5 minutes and heat on low. This will also soften the slime.
Option 1: You will want to keep it stored in a tight plastic container with a lid or a Zip-loc bag. Also, kneading the slime will help soften it up once you take it out of  the container.
Answer: 1