Mix together chili powder, brown sugar, garlic, Worcestershire sauce, cumin, and pepper. Make a paste and rub over brisket.
Place brisket into slow cooker.
Mix together beef broth, liquid smoke, onions and chili sauce.
Pour over brisket.
Cover and cook on low for 7-8 hours or high 4-5 hours or until fork tender and meat easily pulls apart. I highly recommend cooking it on low if at all possible for the best, most tender results.
Remove brisket from cooker and slice across the grain into thin slices.
Top with favorite BBQ sauce if desired or spoon some of the leftover pan juices over meat.
Video
Notes
To cook in the instant pot:
Cover meat with rub and place in the Instant Pot.
Add in liquid.(using 1 cup of beef broth)
Put on the lid and cook on meat/stew setting for 90 minutes.
Do a 10 minute natural release and then a quick release.