Stir the rub ingredients together in a small bowl.
Pat the brisket dry and season all over with the rub, pressing to adhere.
In the bottom of a 6 to 8 quart slow cooker, whisk barbecue sauce with the beef broth.
Place the brisket on top.
Cover and cook on Low for 8-10 hours, until the brisket is fork tender and an instant-read thermometer in the thickest part reads about 94 to 96°C (201 to 205°F).
Transfer the brisket to a foil-lined sheet pan.
Brush with some of the barbecue sauce.
Broil for 5 to 10 minutes until slightly caramelized, watching closely.
Warm the remaining sauce if needed.
Allow the brisket to rest for 20-30 minutes, then slice thinly against the grain and serve with sauce on the side.