Steps

1. Preheat the oven to 350 degrees. Use ungreased cookie sheets.
2. Combine the baking soda, peanut butter, salt, and warm water in a bowl, and stir vigorously until well blended. Add 1½ cups of the flour and mix well. Add more flour if the dough is too tacky to manage; it should be rather stiff and coarse.
3. Turn out onto a lightly floured surface and roll out to a thickness of about 0.0625 inch. Trim the dough to fit your cookie sheet and, using your hands and a spatula, transfer the dough to the cookie sheet. With a knife, score the dough into rectangles 2 inches by 1½ inches, not cutting all the way through.
4. Bake for 7 minutes. Turn the cracker sheet over and bake for another 5 to 7 minutes, or until the crackers feel firm and crisp. Remove from the oven and cool on racks. Break into individual crackers and serve.