Preheat the oven to 400°F (200°C) and line two baking sheets with parchment paper.

In a large mixing bowl, whisk together 2 cups all-purpose flour, 1/4 teaspoon baking soda, and 1 teaspoon of the sea salt until evenly combined.

Pour 3/4 cup water and 4 tablespoons melted butter into the flour mixture and stir until a shaggy dough forms.

Turn the dough out onto a lightly floured surface and knead for about 2 minutes until smooth and elastic.

Cover the dough with plastic wrap and let rest for 5 minutes to relax the gluten.

Divide the dough in half and roll one portion at a time into a thin sheet about 1/16 inch thick.

Using a knife or pizza cutter, cut the dough into 2-inch squares and transfer them to the prepared baking sheets.

Prick each square 3-4 times with a fork, then sprinkle the remaining 1/2 teaspoon sea salt over the crackers.

Bake for 20-25 minutes, rotating the sheets halfway through, until the crackers are golden brown and crisp.

Let the crackers cool on the baking sheets for 5 minutes, then transfer to a cooling rack to cool completely.