I have wanted to make some for about a year now. I finally got around to trying it. Turns out, it's really easy (and cheap) to make. In fact, you only need three ingredients.
4 1/2 cups flour
2 cups water
2 1/2 tsp. salt
Mix all ingredients and then roll out on a floured board into a rectangle of about 1/2 inch thickness. Cut into smaller squares and poke holes in each one with a fork on both sides.
Readers, would you want to try hardtack?