Crockpot BBQ Sweet and Smokey Chicken

1 broiler-fryer chicken, cut in serving pieces
1/2 cup water
1 teaspoon hickory smoked salt or hickory flavored meat rub
1 large onion sliced
1/4 teaspoon pepper

Barbecue Sauce
1/2 cup catsup
1/2 cup cooking oil
1/2 cup maple syrup
2 tablespoons prepared mustard
1/4 cup vinegar

Rub chicken with hickory salt then place in slow cooker. Place onions on top of chicken. Combine barbecue sauce ingredients and pour over top of chicken. Cover and cook on low for 8 to 10 hours.