01 - Combine smoked paprika, brown sugar, kosher salt, black pepper, garlic powder, onion powder, and cayenne pepper in a small bowl. Mix thoroughly until evenly distributed.
02 - Pat the brisket completely dry with paper towels. Apply the dry rub mixture generously over all surfaces, pressing firmly to ensure the spices adhere to the meat.
03 - Place the seasoned brisket in the slow cooker with the fat side facing up. This allows the fat to render down and baste the meat during cooking.
04 - Whisk together ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, liquid smoke, garlic powder, and onion powder in a separate bowl until completely smooth.
05 - Pour half of the BBQ sauce evenly over the brisket. Cover and cook on low setting for 8 hours until the meat is fork-tender and easily pulls apart.
06 - Carefully transfer the cooked brisket to a cutting board. Allow it to rest for 10 minutes before slicing against the grain to ensure tenderness.
07 - Skim and discard excess fat from the cooking liquid remaining in the slow cooker.
08 - Arrange the sliced brisket on a serving platter. Serve with the reserved BBQ sauce on the side for guests to add as desired.