01 - Coat beef short ribs evenly with salt and black pepper on all sides.
02 - In a large skillet over medium-high heat, sear short ribs for 2 to 3 minutes per side until browned. Transfer to the slow cooker.
03 - Add onion, carrots, celery, and garlic to the skillet. Sauté for 3 to 4 minutes until vegetables begin to soften, then transfer to the slow cooker.
04 - Pour beef broth and red wine into the slow cooker. Stir in tomato paste and Worcestershire sauce.
05 - Arrange thyme sprigs, rosemary sprigs, and bay leaves in the slow cooker.
06 - Cover and cook on LOW for 8 hours, until ribs are extremely tender and the meat easily separates from the bone.
07 - Remove herb sprigs and bay leaves. Skim off excess fat from the surface, if necessary.
08 - For a thicker sauce, mix cornstarch with water until smooth and stir into the slow cooker. Set to HIGH and cook for 10 to 15 minutes, or until sauce reaches desired consistency.
09 - Serve short ribs hot with sauce and vegetables.