1. Generously season the brisket with the dry rub on all sides.  Wrap in plastic wrap and refrigerate overnight.
2. Heat a large skillet (better yet, a Dutch oven) over medium-high heat and sear the brisket until browned on all sides. Remove from the skillet and set aside.
3. In the same skillet, sauté the sliced onion and minced garlic until softened and fragrant, approx. 4 minutes.
4. Place a rack or a layer of vegetables (onions, carrots, or celery) in the bottom of the slow cooker to elevate the brisket.
5. Place the seared brisket on top of the rack or vegetables in the slow cooker.
6. In a small bowl, whisk together beef broth, Worcestershire sauce, soy sauce, brown sugar, Dijon mustard, smoked paprika, dried thyme, and black pepper.
7. Pour the onion and garlic mixture over the brisket in the slow cooker, followed by the liquid mixture.
8. Cover the slow cooker and cook on low heat for 8-10 hours or on high heat for 4-6 hours, until the brisket is tender and easily pulls apart with a fork. NOTE: If you find there is too much liquid accumulating, use a turkey baster and remove the excess liquid.
9. Once cooked, remove the brisket from the slow cooker and let it rest for a few minutes before slicing against the grain.
10. Optional: You can strain the cooking liquid and simmer it on the stovetop to reduce and thicken it into a sauce.
11. Serve the sliced brisket with the sauce on the side, alongside your favorite sides like mashed potatoes, roasted vegetables, or coleslaw.

Elevating the brisket will help ensure that it doesn’t sit in the accumulated juices during the cooking process, leading to a more desirable texture. Enjoy your slow-cooked beef brisket!

FOR THE BBQ SAUCE:

1. Strain the leftover cooking liquid from the slow cooker into a saucepan, discarding any solids.
2. Place the saucepan with the cooking liquid over medium heat.
3. Add the ketchup, apple cider vinegar, brown sugar, Dijon mustard, Worcestershire sauce, smoked paprika, garlic powder, onion powder, black pepper, and a pinch of salt.
4. Stir well to combine all the ingredients.
5. Bring the mixture to a simmer and let it cook for about 10-15 minutes, stirring occasionally, until the sauce thickens and the flavors meld together.
6. Taste the sauce and adjust the seasoning, adding more salt, sugar, or any other desired flavors to your preference.
7. Once the sauce reaches your desired consistency, remove it from the heat and let it cool slightly.
9. Transfer the BBQ sauce to a jar or airtight container and refrigerate until ready to use.