Pat beef with paper towels to remove excess moisture. Toss with 3 tbsp flour until coated.
Heat a large non-stick frying pan over medium-high. Add 2 tsp oil, then beef. Cook until brown on all sides, about 5 minutes. Transfer to slow cooker.
Add remaining oil to pan, then add onion and garlic and cook for 3 minutes. Transfer to slow cooker along with carrots, potato, broth, tomato paste, mushrooms, thyme and salt. Stir well. Add bay leaves. Cover and cook on low until beef is tender, 6 to 8 hours.
Remove and discard bay leaves. Stir in peas and Worcestershire.
Serve over rice, with bread, or freeze for later.