01 - Generously season the beef short ribs with salt and pepper on all sides.
02 - Heat a large skillet over medium-high heat. Sear the beef short ribs on all sides, 2 to 3 minutes per side, until evenly browned. Transfer the ribs to the slow cooker.
03 - Add onion, carrots, celery, and garlic to the skillet. Sauté for 3 to 4 minutes until vegetables are slightly softened, then transfer to the slow cooker.
04 - Pour in the beef broth and red wine. Stir in the tomato paste and Worcestershire sauce until incorporated.
05 - Place the thyme, rosemary, and bay leaves into the slow cooker on top of the other ingredients.
06 - Set the slow cooker to LOW. Cover and cook for 8 hours, or until the short ribs are extremely tender and meat separates easily from the bone.
07 - Remove thyme, rosemary, and bay leaves. Skim excess fat from the sauce as needed.
08 - For a thicker sauce, mix cornstarch and water, then stir into the cooking liquid. Set the cooker to HIGH and cook for another 10 to 15 minutes until the sauce has thickened.
09 - Plate the short ribs with the sauce and vegetables, served hot.