To freeze the meatballs, roll the mixture into balls and place them on a parchment paper lined baking sheet. Place the sheet in the freezer for 60 minutes. After 60 minutes, remove the sheet and place the meatballs in a large ziplock bag. They will stay good for about 6 months! When ready to use in the slow cooker, place them in the sauce and cook for 8 to 10 hours on low heat.