01 - Pat brisket dry with paper towels. Combine salt, pepper, smoked paprika, garlic powder, onion powder, and cayenne in a small bowl. Rub spice mixture evenly over entire surface of brisket.
02 - Heat olive oil in a large skillet over medium-high heat. Sear brisket on all sides until deeply browned, approximately 2 to 3 minutes per side.
03 - Place seared brisket into slow cooker, fat side up if applicable.
04 - In a mixing bowl, whisk together ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, onion powder, black pepper, and sea salt until smooth and fully incorporated.
05 - Pour half of prepared BBQ sauce over brisket in slow cooker, reserving remaining sauce for serving. Cover and cook on LOW for 8 hours or HIGH for 4 to 5 hours, until meat is fork-tender and shreds easily.
06 - Transfer cooked brisket to cutting board. Allow to rest for 10 minutes, then slice against the grain or shred with two forks.
07 - Skim excess fat from sauce remaining in slow cooker. Return sliced or shredded brisket to pot, tossing to coat with defatted sauce. Serve immediately with reserved BBQ sauce on the side.