Begin by lightly seasoning the chicken breasts with salt and pepper. Pat the chicken dry with paper towels before seasoning.
In a large bowl, combine the herb-seasoned stuffing mix with the melted butter and chicken broth. Stir in the diced celery and onion until well combined.
Place the seasoned chicken breasts at the bottom of the slow cooker. Spread the stuffing mixture evenly over the top of the chicken.
Cover the slow cooker and cook on low for 6 to 8 hours or on high for 4 to 5 hours. The chicken is done when it reaches an internal temperature of 165°F.
Once cooked, shred the chicken directly in the slow cooker using two forks, mixing it with the stuffing.