1. Pat the beef cubes dry with paper towels and season generously with salt and pepper. 2. Heat olive oil in a large skillet over medium-high heat. Brown the beef in batches on all sides. Remove beef and set aside. 3. Add onion, carrots, and celery to the skillet. Sauté until softened, about 5-7 minutes. 4. Stir in the tomato paste, thyme, and rosemary. Cook for 1 minute. 5. Deglaze the skillet with red wine (if using), scraping up any browned bits from the bottom. Cook until liquid is reduced by half. 6. Transfer the beef and vegetable mixture to a 6-quart (or larger) slow cooker. 7. Pour in the beef broth and Worcestershire sauce. Add the bay leaves. Stir well. 8. Cover and cook on low for 6-8 hours or on high for 3-4 hours, or until beef is fork-tender. 9. During the last hour of cooking, stir in the quartered potatoes. 10. In a small bowl, whisk together the flour with 1/4 cup of the stew liquid to form a slurry. Stir the slurry into the stew to thicken. Cook for another 30 minutes, or until desired thickness. 11. Remove bay leaves. Taste and adjust seasoning with salt and pepper as needed. 12. Garnish with fresh chopped parsley before serving.