Fry bacon until crisp in a saucepan large enough for making soup. Remove bacon. Add onion and saute until limp. Add potatoes, carrots, boiling water and salt. Cover and cook until vegetables are tender, 8 to 10 minutes. Add seasonings. Blend flour with 1/4 cup of milk and add with the remaining milk to the vegetable mixture, stirring constantly. Heat until slightly thickened. Crumble bacon and sprinkle over the soup.