Preheat your oven to 400°F (200°C) and line two large baking sheets with parchment paper.
In a large bowl, whisk together 2 cups all-purpose flour, 1 teaspoon baking soda, and 1 teaspoon fine sea salt until well combined.
In a small bowl, melt 4 tablespoons unsalted butter, then stir in 1/2 cup cold water.
Pour the butter-water mixture into the flour mixture and mix until a shaggy dough forms.
Turn the dough onto a lightly floured surface and knead for 2–3 minutes until it forms a smooth ball.
Divide the dough into two equal pieces.
On a lightly floured surface, roll one piece as thinly as possible (about 1/16 inch).
Use a pizza cutter or sharp knife to cut the rolled dough into roughly 1½-inch squares and transfer them to the prepared baking sheet.
Repeat rolling and cutting with the second piece of dough.
Use a fork to prick (dock) holes all over each cracker.
Lightly brush the tops of the crackers with a little water, then sprinkle generously with coarse sea salt.
Bake for 10–15 minutes, or until golden brown and crisp, rotating the baking sheets halfway through if needed.
Transfer the crackers to a wire rack and let them cool completely.
Store in an airtight container at room temperature for up to one week.