Step 1: It is essential to cook very slowly. A slow cooker is ideal. Cover the liver with water and slow cook for about 6 hours. Thicken with flour about 1 hour before end. Add salt to taste. Any left over may be frozen but be warned. If reheated in a microwave too violently the liver may explode. 50 years ago, in the Army, the blokes used to go mad over this delicious dish. The cooks used to cook it on the range over-night.