01 - Season beef cubes evenly with salt and freshly ground black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Brown the beef cubes in batches, approximately 3 to 4 minutes per batch, until all sides are seared. Transfer browned beef to the slow cooker.
03 - Place carrots, potatoes, celery, onion, and garlic into the slow cooker atop the seared beef.
04 - In a mixing bowl, whisk together beef broth, tomato paste, Worcestershire sauce, and red wine if using. Pour the mixture evenly over the beef and vegetables in the slow cooker.
05 - Incorporate dried thyme, rosemary, and bay leaves. Gently stir to combine all ingredients.
06 - Cover and cook on low heat for 8 hours or on high for 4 to 5 hours, until beef is tender and vegetables are cooked through.
07 - Thirty minutes before serving, blend cornstarch or gluten-free flour with water to create a slurry. Stir this into the stew, then add frozen peas. Cover and continue cooking for 30 minutes until the stew has thickened.
08 - Remove bay leaves before serving. Adjust seasoning with salt and pepper to taste.