Fill the large ziploc halfway with ice cubes and add 1/4-1/2 cup of salt. You can use rock salt (works best) or table salt (still works well).
In the small bag, put 1.5 cups of your favorite milk, reduced fat milk, or heavy cream. Add two tablespoons of sugar for every 1.5 cups of milk (or to taste).
Seal the smaller bag then place it in the big bag and SHAKE IT. This is where the kids can help! They can (gently) shake, rock, spin, toss, and play with the bag. It takes about 5-7 minutes of good shaking to get to the right consistency.
Congrats! You have made your first ice cream! Serve it up right out of the bag if you want to (just rinse the salt off the outside beforehand).