Gradually add water until the dough sticks together - you may not need the entire 2 cups.
Knead the dough by hand.
Shape into a rectangle and roll out with a rolling pin to about 1/2" thick.
Cut into 3" x 3" squares using a knife or cookie cutter.
Poke 4 rows of 4 holes into each piece using a nail, toothpick or chopstick. Flip and repeat on the other side taking care not to puncture right through.
Arrange on an ungreased cookie sheet and bake for 30 minutes.
Turn each piece and bake for another 30 mins.
Cool & store in a cool, dark place.
Notes
Make sure you soak your hardtack to soften before eating so you don't break a tooth!