01 - Pat the chuck roast dry with paper towels and generously season all sides with kosher salt and black pepper.
02 - Heat a large skillet over medium-high heat. Sear the seasoned roast on all sides until well browned, about 4 minutes per side. Carefully transfer the seared roast to the slow cooker.
03 - Arrange the carrots, potatoes, celery, and onion around and beneath the beef within the slow cooker insert.
04 - Distribute the minced garlic, fresh thyme sprigs, fresh rosemary sprigs, and bay leaves evenly over the roast and vegetables.
05 - In a small bowl, whisk together the beef broth, Worcestershire sauce, and tomato paste (if using). Pour this complete liquid mixture over the meat and vegetables in the slow cooker.
06 - Cover the slow cooker with its lid and cook on the LOW setting for 8 hours, or continue until the beef is exceptionally fork-tender and the vegetables are thoroughly cooked through.
07 - Carefully remove the cooked roast and vegetables from the slow cooker and transfer them to a serving platter. Discard the bay leaves and any tough herb stems.
08 - For a richer, thicker gravy, mix 2 tablespoons of cornstarch with 2 tablespoons of cold water to create a smooth slurry. Stir this slurry into the residual cooking liquid in the slow cooker. Increase the setting to HIGH and cook for an additional 5 minutes until the gravy reaches the desired thickened consistency.
09 - Serve the beef, sliced or shredded, accompanied by the tender cooked vegetables and the savory gravy.