Process cheddar cheese, flour, cornstarch, and salt together in a food processor until combined, about 30 seconds. Add butter and process until mixture resembles wet sand, about 20 seconds. Add water and pulse until dough forms large clumps, about 10 pulses.

Transfer dough to a lightly floured work surface. Divide in half and pat each into a 6-inch square. (No need to use a rolling pin, just pat with hands.) 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 (177°C). Line 2 large baking sheets with parchment paper or silicone baking mats.

Unwrap each dough square. Place each on a lightly floured work surface and roll out into a 9-inch square. Doesn’t need to be perfect! Using a fluted pastry wheel, pizza cutter, or small sharp knife, trim dough into a neat 8 inch square. Slice square into 8 strips, each 1 inch wide, then make 8 perpendicular slices, each 1 inch wide. Each 8-inch square will have 64 squares (crackers).

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, if desired. Bake until golden brown around the edges, about 16-18 minutes, rotating the baking sheets halfway through baking. For crunchier crackers, bake for 20 minutes.

Remove from the oven and cool completely on the baking sheet before serving.

Store leftover crackers at room temperature for up to 1 week. If tightly sealed, they’ll lose their crunch. Feel free to keep the lid slightly ajar to maintain some crunchiness.