01 - Arrange sliced onion and minced garlic evenly across the bottom of the slow cooker insert.
02 - Whisk together beef broth, tomato paste, and Worcestershire sauce in a small bowl until smooth and fully combined.
03 - Combine chili powder, cumin, smoked paprika, oregano, salt, black pepper, and cayenne in a small dish. Rub the spice mixture thoroughly over all surfaces of the chuck roast, pressing gently to adhere.
04 - Place the seasoned roast directly on top of the onion and garlic bed in the slow cooker.
05 - Pour the broth mixture evenly over the beef and onions.
06 - Cover with the lid and cook on low heat for 8 hours until the beef is fork-tender and easily shreds apart.
07 - Transfer the cooked roast to a cutting board. Using two forks, pull the meat apart into shreds. Return the shredded beef to the slow cooker and toss with the cooking juices.
08 - Serve hot in tacos, over rice, in sandwiches, or as desired.