In ungreased 8 or 9 inch cake pan stir together flour, sugar, cocoa, baking soda, and salt. Spread dry ingredients out in pan and make 3 depressions in mixture with your spoon. In one hole, place vanilla. In second place vinegar. In third place melted shortening. Pour water over all. Now mix it all up with a spoon. Be sure to get corners. Bake at 350 degrees for about 30 minutes until cake shrinks from sides of pan. Frost with chocolate frosting.