Preheat your oven to 400°F (200°C)
In a large bowl, mix together the ground beef, egg, breadcrumbs, garlic, onion, salt, and pepper.
Shape the mixture into round balls, about 1-½ inches in diameter, by rolling them between your palms. 1 lb of ground meat will make approximately 20 meatballs.
Place them on a large baking sheet. (Line it with parchment paper for easy cleanup.)
Bake the meatballs for 18-20 minutes, or until they turn golden brown.
While the meatballs are baking, prepare the sauce. In a medium bowl, combine the cranberry sauce, tomato paste, apple cider vinegar, brown sugar and the hot sauce. Mix well.
After baking, let the meatballs cool for 10 minutes.
In a slow cooker set to high heat, add a layer of meatballs and top with half of the sauce. Add the remaining meatballs and sauce, ensuring they are well coated.
Cook on high for 3 hours or on low for 6 hours, stirring occasionally.