Preheat oven to 350 degrees F (175 degrees C). Line a large baking pan with aluminum foil and spray with cooking spray.
Place ribs onto the prepared baking sheet. Season both sides with grill seasoning.
Bake ribs in the preheated oven for 30 minutes; flip ribs over and bake an additional 15 minutes. Cut ribs apart and place into a slow cooker.
Mix ketchup, brown sugar, Worcestershire sauce, Dijon mustard, and garlic in a bowl until thoroughly combined; pour sauce over ribs. Stir to coat. Cook ribs on Low until tender, 4 to 6 hours; stir occasionally.
