In a small bowl, combine brown sugar, paprika, chili powder, garlic powder, onion powder, cayenne, salt, and pepper to create a dry rub.
Rub the seasoning mixture onto all sides of the brisket, pressing firmly to adhere.
Pour the beef broth, Worcestershire sauce, and liquid smoke into the bottom of a 6-quart slow cooker.
Place the seasoned brisket into the slow cooker (fat side up if applicable).
Cover and cook on the LOW setting for 8 to 10 hours, or until the meat is fork-tender.
Carefully remove the brisket from the slow cooker and let it rest on a cutting board for 15 minutes.
Slice the beef against the grain into 1/4-inch thick slices.
Skim the excess fat from the liquid in the slow cooker, then stir in the BBQ sauce to create a glaze.
Return the sliced meat to the slow cooker to coat in the sauce or serve the sauce on the side.