Clean and chop the vegetables. Bring the water with salt to a boil. First add potatoes, a little later carrots and peas and then cauliflower. Let everything simmer on a low flame for about 10 minutes, the vegetables should still be a little hard.
Mix the flour with the milk and add this mix to the soup, cover and simmer again for about 10 minutes. Season to taste with salt, pepper and herbs.