01 - Pat the beef chuck roast dry and season all sides evenly with kosher salt and black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Sear the roast for 3 to 4 minutes per side until browned. Transfer to the slow cooker.
03 - Place the potatoes, carrots, and sliced onion around the beef in the slow cooker.
04 - In a bowl, whisk together beef broth, tomato paste, Worcestershire sauce, garlic, thyme, and rosemary. Pour over the beef and vegetables. Add bay leaves.
05 - Cover and cook on LOW for 8 hours, or until beef is tender and vegetables are soft.
06 - Remove bay leaves. Transfer beef to a cutting board and shred or slice as preferred.
07 - For a thicker sauce, whip cornstarch and cold water into a slurry, stir into the slow cooker, cover, and cook on HIGH for 10 to 15 minutes until thickened.
08 - Plate the beef with carrots and potatoes, spooning the sauce over the top.