01 - Arrange 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 dish. Rub the mixture thoroughly over all surfaces of the chuck roast.
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, ensuring some liquid reaches the bottom.
06 - Cover and cook on low heat for 8 hours, or until the beef pulls apart easily with a fork.
07 - Transfer the cooked beef to a cutting board. Using two forks, shred the meat into strands. Return the shredded beef to the slow cooker and toss well with the cooking juices.
08 - Serve hot in tacos, sandwiches, rice bowls, or as desired.