01 - Sprinkle short ribs evenly on all sides with salt and black pepper.
02 - Heat a large skillet over medium-high and sear the beef short ribs on all sides for 2–3 minutes per side until well browned. Transfer the browned ribs to the slow cooker.
03 - Add onions, carrots, celery, and garlic to the same skillet. Cook for 3–4 minutes over medium heat, stirring occasionally, until vegetables are slightly softened. Add them to the slow cooker.
04 - Pour beef broth and red wine into the slow cooker. Stir in tomato paste and Worcestershire sauce until combined.
05 - Nestle thyme, rosemary, and bay leaves among the beef and vegetable mixture in the slow cooker.
06 - Cover and cook on LOW for 8 hours, until the meat is very tender and easily separates from the bone.
07 - Remove and discard herb sprigs and bay leaves. Skim excess fat from the surface if desired.
08 - For a richer sauce, stir in cornstarch slurry and cook on HIGH for 10–15 minutes until the sauce thickens.
09 - Serve the beef short ribs hot with sauce and cooked vegetables.