Place the frozen meatballs in your slow cooker.
In a medium bowl, whisk together the orange marmalade, soy sauce, ketchup, apple cider vinegar, brown sugar, minced garlic, ground ginger, and red pepper flakes.
Pour the mixture over the meatballs, ensuring they are evenly coated.
Cover and cook on low for 4-6 hours or on high for 2-3 hours, until the meatballs are heated through and the sauce is bubbling.
Stir the meatballs occasionally to keep the sauce well mixed.
Once done, give the meatballs a gently stir to make sure they’re fully coated in the sauce. Serve them hot, garnished with some chopped fresh parsley if you like.
