01 - Generously season beef short ribs with salt and black pepper on all surfaces.
02 - Heat a large skillet over medium-high heat. Sear short ribs for 2 to 3 minutes per side until well browned, then transfer to the slow cooker.
03 - In the same skillet, sauté onion, carrots, celery, and garlic for 3 to 4 minutes until slightly softened. Add vegetables to the slow cooker.
04 - Pour in beef broth and red wine. Stir in tomato paste and Worcestershire sauce until well combined.
05 - Add thyme sprigs, rosemary sprigs, and bay leaves to the slow cooker.
06 - Cover and cook on low for 8 hours, or until beef is extremely tender and meat separates easily from bone.
07 - Discard herb sprigs and bay leaves. Skim excess fat from sauce as needed.
08 - For a thicker sauce, combine cornstarch and water, then stir into the slow cooker. Cook on high for 10 to 15 minutes until the sauce reaches desired consistency.
09 - Plate beef short ribs hot with sauce and vegetables. Serve immediately.