In a small bowl, mix together the brown sugar, salt, pepper, garlic powder, onion powder and smoked paprika.
Coat a large slow cooker with cooking spray. Roll a piece heavy duty aluminum foil into a ring shape to fit into the slow cooker as a rack.
Place the chicken on top of the foil ring. Rub the spice mixture all over the chicken.
Cover and cook on HIGH for 3-4 hours or until thermometer inserted into the thickest part of the thigh registers at 165 degrees or higher.
Transfer the chicken to a sheet pan or baking dish and broil in the oven for 4-5 minutes or until chicken skin is brown and crispy. Serve.