Cut steak into serving-size pieces. Sprinkle with salt and pepper. Place in a crockpot. Add dill, onion, bouillon cube and 1/2 cup water. Cover and cook on low for 6 to 8 hours. Remove meat. Thicken juices with flour dissolved in 1/4 cup cold water. Turn control to high; cook 10 minutes or until slightly thickened. Stir in sour cream. Turn off the heat. Serve sauce over meat, with mashed potatoes or noodles.