Preheat oven to 375 degrees.
Mix the flour, water, and salt in a bowl.
After mixing completely, the dough should be a little dry (and not stick to your fingers). If your mix is still too sticky, you can add more flour in small increments until the dough is dry enough.
Use a roller to spread out the dough on a counter, large cutting board, etc. until it reaches a thickness of roughly 1/3 to 1/2 inch. To prevent sticking to the counter or cutting board, you should spread a little flour on the surface before rolling the dough. Also spread a little flour on top of the dough to prevent the roller from sticking to the dough.
Cut the dough into squares (e.g., 3-inch squares). You can create square hardtack “biscuits” by cutting the dough horizontally & vertically on a large cutting board.
Poke narrow holes in the hardtack biscuits with a chopstick or fork. The holes should go all the way through to the other side of the hardtack. This prevents the hardtack from puffing up.
Place the hardtack biscuits on a baking sheet/tray. Put the baking sheet into the oven and bake for 30 minutes at 375 F. (Wear oven mitts.)
Flip the hardtack over with a spatula and bake for another 30 minutes. Wear oven mitts.
Remove the baking sheet from the oven. Wear oven mitts. Then use a spatula to remove the hardtack from the baking sheet. Place the hardtack biscuits on a cooling rack in order to cool down.
When completely cooled, store the hardtack in an airtight container.
