Make the sauce: In a bowl, whisk together ketchup, tomato paste, apple cider vinegar, maple syrup, Worcestershire, Dijon, smoked paprika, chili powder, garlic powder, onion powder, red pepper flakes, black pepper, salt, and chicken broth.
Add to slow cooker: Place the chicken in the slow cooker in an even layer.
Pour the sauce over the top, turning the pieces once so they’re coated.
Cook low and slow: Cover and cook on Low for 4 to 5 hours, or on High for 2 to 3 hours. Do not overcook or the chicken can turn stringy.
Shred the chicken: Transfer the cooked chicken to a large plate or cutting board. Shred with two forks into bite-size pieces.
Reduce and balance the sauce: If the sauce looks thin, remove the lid and let it simmer in the slow cooker on High for 10 to 15 minutes, or transfer to a saucepan and simmer. Taste and adjust salt, vinegar, or sweetness as needed.
Combine: Return shredded chicken to the slow cooker and toss with the thickened sauce until evenly coated.
Serve: Pile onto whole-grain buns with crunchy slaw, spoon over rice or cauliflower rice, tuck into lettuce wraps, or layer into baked sweet potatoes.