In a 2-4 quart slow cooker, whisk together cranberry sauce, honey, vinegar, broth, corn starch, garlic, salt and pepper flakes until combined (may still have a few lumps).
Add the meatballs and stir to coat.
Cover and cook on low for 4-6 hours or high for 2-3 hours, until meatballs are heated through and sauce has thickened.
Serve alone as an appetizer or over rice or mashed potatoes.