Mix the sauce base. In a bowl, whisk together BBQ sauce, chicken broth, brown sugar, apple cider vinegar, Worcestershire, smoked paprika, garlic powder, onion powder, pepper, and salt. Add heat now if you like it spicy.
Layer the chicken. Place chicken breasts (or thighs) in the bottom of the slow cooker in an even layer.
Pour the sauce over the top, coating the chicken.
Cook low and slow. Cover and cook on LOW for 4–6 hours (best texture) or HIGH for 2.5–3.5 hours, until the chicken is fork-tender and shreds easily.
Shred the chicken. Transfer chicken to a cutting board and shred using two forks. Return the shredded chicken to the slow cooker and toss with the sauce.
Adjust and finish. If the mixture looks thin, let it cook uncovered on HIGH for 10–15 minutes to reduce. For extra gloss and flavor, stir in 2–4 tablespoons more BBQ sauce to taste.
Serve your way. Spoon onto toasted buns with coleslaw and pickles, or use in tacos, quesadillas, rice bowls, baked potatoes, or salads.