Pat the beef brisket dry with paper towels. In a small bowl, combine all the dry rub ingredients (brown sugar, paprika, garlic powder, onion powder, mustard powder, cumin, chili powder, salt, and pepper). Rub the spice mixture generously all over the surface of the meat.

Briefly sear the beef in a hot skillet with a tablespoon of olive oil, fat-side down first, for 2-3 minutes per side. This step locks in flavor and provides exceptional depth.

In the bottom of your 6-quart slow cooker, whisk together the BBQ sauce, apple cider vinegar, Worcestershire sauce, and liquid smoke (if using).

Place the seasoned and optionally seared brisket into the slow cooker, fatty side up.

Cook on LOW for 8 to 10 hours, or on HIGH for 4 to 5 hours. The brisket is done when it easily shreds with a fork—it should almost fall apart when tested.

Carefully remove the brisket from the slow cooker and place it on a large cutting board. Use two forks to shred the meat, or let it rest for 10 minutes before slicing thinly against the grain.

Transfer the shredded or sliced meat back into the slow cooker liquid. Stir to coat thoroughly, allowing the meat to absorb the rich BBQ flavors for another 15 minutes on the Keep Warm setting.