Place prepared brussels sprouts, carrots, and maple syrup in slow cooker.
Heat a skillet over medium-high heat. Add bacon and onion to hot skillet, and saute until most fat is rendered from bacon and onions are browning. Turn off heat. Use a slotted spoon to scoop cooked onions and bacon into slow cooker with vegetables. (Do not discard oil yet.) Stir contents of slow cooker well.
Heat same skillet with bacon drippings over medium heat. Sprinkle chicken on both sides lightly with seasoned salt. Cook chicken in hot oil for about 5 minutes on each side. Place chicken on top of vegetables.
Pour cider over the chicken and vegetables, and cover. Cook on high 6 hours or low 8 hours.