Combine the rub ingredients in a small bowl; chili powder, garlic powder, celery seed & pepper.
Rub onto the meat.
OPTIONAL: Cover it in plastic wrap and pop it in the fridge overnight to really deepen the flavors.
Place brisket into bottom of the crock pot. Combine all the sauce ingredients and stir together well.
Pour sauce all over the brisket, coating evenly.
Cover and cook on low for about 6-8 hours.
Remove meat and cut the brisket across the grain, making thin slices.
Most grocery stores label flat end trimmed beef brisket just as "brisket." The only time you really see specific labeled cuts of meats are at higher end supermarkets or at butcher shops. In which case, you'll want to specifically ask for this particular cut. For extra flavor: Drizzle a bit of the liquid that is left in the slow cooker on top of the cuts of meat. When you cut across the grain, it gives you a tender cut of meat.