01 - Pat beef cubes dry with paper towels; season generously with salt and black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Brown the beef in batches, searing all sides. Transfer seared beef to the slow cooker.
03 - Place carrots, potatoes, celery, onion, and garlic into the slow cooker with the beef.
04 - In a small bowl, whisk together all-purpose flour and ½ cup beef broth until smooth, then pour into the slow cooker.
05 - Add remaining beef broth, red wine (if using), tomato paste, Worcestershire sauce, thyme, rosemary, and bay leaves. Stir to combine all ingredients.
06 - Cover and cook on low for 8 hours or on high for 4–5 hours, until beef is fork-tender and vegetables are soft.
07 - Remove bay leaves, stir in frozen peas, and cook for an additional 10 minutes.
08 - Taste and season with additional salt and pepper as needed. Serve immediately while hot.