01 - Season the beef chuck roast evenly with kosher salt and black pepper.
02 - Place sliced onion, carrots, celery, and smashed garlic cloves into the base of the slow cooker.
03 - Set the seasoned beef roast atop the vegetables. Sprinkle dried thyme, dried rosemary, and add the bay leaf over the roast.
04 - Pour beef broth and Worcestershire sauce evenly over the roast and vegetables.
05 - Cover and cook on low heat for 8 hours until the beef is tender and easily pulls apart with a fork.
06 - Transfer the roast and vegetables to a serving platter and tent loosely with foil to retain warmth.
07 - Skim excess fat from the cooking liquid remaining in the slow cooker.
08 - Combine cornstarch or all-purpose flour with water in a small bowl to create a smooth slurry, then stir into the cooking liquid.
09 - Set the slow cooker to high and cook uncovered for 10 to 15 minutes, stirring occasionally, until the gravy thickens.
10 - Slice or shred the roast beef and serve alongside the cooked vegetables, spooning the thickened gravy over the top.