Preheat oven to 425 degrees.
Mix dry ingredients together with the shortening using a pastry blender (or food processor) until crumbly like sand.
Stir in the milk until the dough comes together. It will be somewhat crumbly but can be pressed together.
Turn out on a well-floured surface and knead until the dough comes together. Then, fold the dough over, press it together slightly, turn 1/4 round, and fold again. Repeat several times to create a lighter, flaky cracker.
Roll out until the dough is thin, about 2 centimeters. (Leaving the cracker thicker will impact the baking time but would still be delicious.) Cut into the shape you desire and prick with a fork.
Place on a nonstick baking sheet or parchment lined baking sheet. Sprinkle with kosher or sea salt.
Bake for about ten minutes but keep a careful eye as the thickness will impact the bake time. The crackers are ready when they are lightly colored and flaky. Remove from the oven and allow to cool on the baking sheet.
Once cooled, store in an airtight container.