01 - Sprinkle beef short ribs evenly with salt and pepper on all sides.
02 - Heat a large skillet over medium-high. Sear short ribs on all sides until well-browned, about 2 to 3 minutes per side. Transfer to the slow cooker.
03 - In the same skillet, add onion, carrots, celery, and garlic. Sauté for 3 to 4 minutes until just softened. Transfer vegetables to the slow cooker.
04 - Pour beef broth and red wine into the slow cooker. Stir in tomato paste and Worcestershire sauce until well combined.
05 - Tuck thyme, rosemary, and bay leaves among the ribs in the slow cooker.
06 - Cover and cook on LOW for 8 hours until the meat is exceptionally tender and nearly falls off the bone.
07 - Discard thyme, rosemary sprigs, and bay leaves. Skim any excess fat from the surface of the sauce.
08 - If a thicker sauce is desired, stir cornstarch and water mixture into the slow cooker. Switch to HIGH and cook 10 to 15 minutes, stirring occasionally, until sauce thickens.
09 - Serve beef short ribs hot, spooning sauce and vegetables over each portion.