Mill Your Flour and chill it for 10 minutes in the freezer.
Use a food processor to combine cheddar cheese, flour, cornstarch, and salt together until combined (about 30 seconds.)
Add cold butter in cubes and process until mixture resembles wet sand, about 20 seconds.
Turn food processor on and add in the cold water one tablespoon at a time.
Transfer dough to a lightly floured work surface. Divide in half and pat each with your hand into into thin squares. If the dough feels dry, moisten your fingers with cold water. Carefully wrap each in plastic wrap and refrigerate until firm, about 45 minutes and up to 2 days.
Preheat oven to 350°F . Line 2 large baking sheets with parchment paper or silicone baking mats.
Unwrap each dough square. Place each on a pastry mat or lightly floured work surface and roll out into a 9-inch square.
Using a fluted pastry wheel, pizza cutter, or small sharp knife, trim dough into a neat 8-inch square. Cut your crackers so they are 1 in by 1 in. You should be able to get 64 crackers from each square.
Place squares on prepared baking sheet. Use a skewer or large toothpick to poke a hole through the center of each. Lightly sprinkle with sea salt. Bake until golden brown around the edges, about 14-16 minutes, rotating the baking sheets halfway through baking. For crunchier crackers, bake for 18 minutes.
Remove from the oven and cool completely on the baking sheet before serving.