Hands On: 20 minutes Total: 8 hours 30 minutes Place onions evenly on bottom of 3 1/2-quart or larger slow cooker. Top with layers of carrots, celery, potatoes and meat; sprinkle with thyme. Pour diced tomatoes with their juice and the water over meat. Cover slow cooker with lid. Cook on LOW 8 to 10 hours (or on HIGH 4 to 5 hours), or until meat is tender. Stir in tomato paste; cover. Cook an additional 10 minutes.