Cut beef pot roast into 12 equal pieces. Place in 4-1/2- to 5-1/2-quart slow cooker. Add onions, tomatoes, potatoes, broth, garlic, thyme, salt, and pepper. Cover and cook on HIGH 5–6 hours, or on LOW 8–9 hours, or until beef is fork-tender. No stirring is necessary during cooking. Stir in broccoli slaw; continue cooking, covered, 30 minutes or until broccoli slaw is crisp-tender. Turn off slow cooker. Stir in peas; let stand, covered, 5 minutes.