Begin by patting the beef short ribs dry with paper towels; season them generously with salt and black pepper on all sides.

In a large skillet, heat olive oil over medium-high heat and sear the ribs for 2-3 minutes on each side until browned. Transfer to the slow cooker.

In the same skillet, sauté the onion and carrots for 3-4 minutes until soft, then add the garlic and cook for an additional 30 seconds. Transfer to slow cooker.

In a bowl, whisk together beef broth, red wine, tomato paste, Worcestershire sauce, soy sauce, and brown sugar. Pour mixture over ribs and vegetables in the slow cooker.

Add thyme, rosemary, and bay leaf to the slow cooker, stirring gently to combine. Cover and cook on low for 7-8 hours or high for 4-5 hours.

Once cooked, remove ribs and strain the liquid if desired. To thicken sauce, mix cornstarch with water and stir into the slow cooker. Return ribs to the sauce before serving.