Place brisket, onions, garlic, beef broth, and liquid smoke in a large crock pot. Cover and turn to low. Cook 8 hours.
Remove brisket and place on a cutting board. Scrape fat off and discard. Shred with two forks.
In a small bowl whisk together seasoning ingredients and pour over shredded brisket and massage it into the meat. Taste and adjust seasonings as needed. Cover immediately until ready to serve as the meat with cool off very quickly.
When you're ready to build your tacos, place you meat in the center of your tortilla or taco shell and top with as many or as few toppings as you like.
Recipe by The Spice Kit Recipes at https://www.thespicekitrecipes.com/slow-cooker-brisket-tacos/