A very simple recipe for hardtack is 2 cups of flour, 1/2 to 3/4 cup water, 6 pinches of salt. Mix all ingredients and press onto a cookie sheet until dough is about 1/2 inch thick. Bake at 400 for about half an hour. After removing from the oven cut into 3 inch square. Poke holes using a fork. Flip the crackers over and bake for another half hour.