01 - Generously season the beef short ribs with salt and black pepper on all sides.
02 - Heat a large skillet over medium-high. Sear the short ribs for 2–3 minutes per side until evenly browned. Transfer the seared short ribs to the slow cooker.
03 - Add chopped onion, carrots, celery, and minced garlic to the skillet. Sauté for 3–4 minutes until the vegetables are just softened, then transfer to the slow cooker.
04 - Pour beef broth and dry red wine into the slow cooker. Stir in tomato paste and Worcestershire sauce until blended.
05 - Arrange thyme sprigs, rosemary sprigs, and bay leaves on top of the beef and vegetables in the slow cooker.
06 - Cover and cook on LOW setting for 8 hours, or until short ribs are fork tender and meat separates from the bone.
07 - Remove and discard herb sprigs and bay leaves. Skim any excess fat from the surface of the sauce.
08 - If a thicker sauce is desired, combine cornstarch with water, and stir the mixture into the slow cooker. Switch to HIGH and cook an additional 10–15 minutes until sauce is thickened.
09 - Portion beef short ribs with their vegetables and sauce, serving hot.