Coat bowl of slow cooker with nonstick cooking spray. Place onion and garlic in bottom of slow cooker. Season ribs with 1 tbsp of the jerk seasoning and place over onion and garlic. Drain pineapple, reserving ¾ cup of the juice, and scatter over ribs. Add green pepper.
Combine reserved pineapple juice, flour and remaining 1 tbsp jerk seasoning. Pour over ribs.
Cover and cook on HIGH for 6 hours or LOW for 8 hours. Stir in beans during last 30 minutes of cooking time. Serve with brown rice and garnish with scallions.