In a small bowl, stir together all of the rub ingredients.
Rinse slabs of ribs and pat dry with paper towels. Remove the thin membrane from the back of the ribs by slicing it and then pulling it off. Reserve 1/2tablespoon of the rub. Sprinkle remaining rub on both sides of the ribs. Wrap in plastic wrap and chill for 8-12 hours.
Combine pineapple juice, vinegar and garlic and reserved rub in a 6 quart slow cooker. Cut the slab of ribs in half and stack in slow cooker. Cover and cook on high for 1 hour. Reduce to low and cook for 5 hours or until tender.
SAUCE: Stir together all ingredients in a small saucepan. Bring to a boil over medium heat, stirring often. Boil for 1 minute. Remove and cover to keep warm.
Preheat broiler with oven rack 10 inches below the heat. Remove ribs from slow cooker and place in a single layer in a foil lined rimmed pan. Brush both sides of ribs with the BBQ sauce and broil for 2-3 minutes on each side until caramelized. Serve with remaining sauce.
Can easily be doubled