Place chicken in the bottom of the slow cooker.
In a medium bowl, whisk together the barbecue sauce, molasses, vinegar, Worcestershire sauce, light brown sugar, pepper, salt, onion powder, and cayenne pepper until combined.
Pour the sauce over the top of the chicken and cook for 2 to 3 hours on high or 4 to 6 hours on low.
Once the chicken is done, remove it from the slow cooker and shred it on a cutting board.
While the chicken is out of the slow cooker, whisk together the cornstarch and water then add to the sauce and whisk to combine.
Add the chicken back into the sauce and stir to combine. Cook on low for an additional 30 minutes so the sauce can soak into the meat and thicken.
Serve warm on a toasted brioche bun with slaw and pickles or use in tacos, quesadillas, and more.