Whisk the Cranberry Glaze: In a medium mixing bowl, whisk together the whole berry cranberry sauce, sweet chili sauce, minced jalapeños, brown sugar, apple cider vinegar, minced garlic, ground cumin, smoked paprika, and kosher salt until well combined and smooth.

Assemble in Slow Cooker: Place the frozen (or freshly browned) meatballs into the bottom of a 4-to-6-quart slow cooker. Pour the cranberry jalapeño glaze evenly over the meatballs, tossing gently with a wooden spoon or spatula until every meatball is thoroughly coated.

Slow Cook to Tender Glazed Perfection: Cover with the lid and cook on LOW for 3 to 4 hours (or on HIGH for 2 hours), stirring occasionally at the halfway mark, until the meatballs are piping hot throughout and the glaze has thickened into a rich, glossy coating.

Garnish & Serve: Switch the slow cooker setting to WARM. Garnish the top with fresh jalapeño rounds and finely chopped cilantro or parsley. Serve directly from the slow cooker with cocktail toothpicks, or transfer to a warm platter for festive holiday buffet entertaining!