In A Large Nonstick Skillet Coated With Nonstick Cooking Spray, Brown Beef On Both Sides. Place Onion And Green Pepper In A 3-Qt. Slow Cooker. Top With Beef. Combine The Broth, Worcestershire Sauce, Dill, Thyme, Pepper And Pepper Flakes; Pour Over Beef. Cover And Cook On High For 3-4 Hours Or Until Meat Reaches Desired Doneness And Vegetables Are Crisp-Tender. Remove Beef And Keep Warm. Combine Cornstarch And Water Until Smooth; Gradually Stir Into Cooking Juices. Cover And Cook About 30 Minutes Longer Or Until Slightly Thickened. Return Beef To The Slow Cooker; Heat Through.