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

Transfer dough to a lightly floured surface. Divide in half and pat each into a 6-inch square using your hands. If the dough feels dry, moisten your fingers with cold water. Wrap each in parchment & refrigerate until firm, about 45 minutes & up to 2 days.

Preheat oven to 350°F. Line 2 large baking sheets with parchment paper or silicone baking mats.

On a lightly floured surface, roll out each dough square into a 9-inch square on your parchment or silicone mat. Trim edges off to make a neat 8 inch square. Slice into 8 strips, each 1 inch wide, then make 8 perpendicular slices, each 1 inch wide. Each 8-inch square will have 64 squares. No need to separate the crackers as they will easily break apart after baking.

Use a skewer to poke a hole through the center of each. Lightly sprinkle with sea salt. 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. Note that they will continue to harden as they cool down after baking. Be careful not to overcook them, as they can burn/overcook very easily

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

Store leftover crackers at room temperature for up to 10 days. If tightly sealed, they'll lose their crunch. Feel free to keep the lid slightly ajar to maintain crunchiness.