01 - Layer the sliced onion and minced garlic evenly across the bottom of the slow cooker insert.
02 - Whisk together the beef broth, tomato paste, and Worcestershire sauce in a small bowl until smooth and fully combined.
03 - Combine the chili powder, cumin, smoked paprika, oregano, salt, black pepper, and cayenne pepper in a small bowl. Massage the spice blend thoroughly over all surfaces of the chuck roast.
04 - Place the seasoned chuck roast directly on top of the onion and garlic bed in the slow cooker.
05 - Pour the broth mixture evenly over the roast, ensuring some liquid reaches the base.
06 - Cover with the lid and cook on low heat for 8 hours until the beef pulls apart easily with a fork.
07 - Transfer the cooked roast to a cutting board. Use two forks to shred the meat into bite-sized pieces, then return it to the slow cooker and toss thoroughly with the accumulated juices.
08 - Serve the shredded beef hot, accompanied by your choice of tortillas, sandwich rolls, or over rice.