Preheat the oven to 500°F.

In a bowl, whisk together the flour, sea salt, sugar, and rosemary until well mixed.

Stir in the olive oil and water, mixing until you achieve a fully combined dough.

Turn the dough out onto a lightly floured piece of parchment paper slightly larger than your baking sheet. Roll until the dough is about 1/8 inch thick.

Trim the edges to ensure even baking, then use a pizza cutter to cut the dough into squares.

Brush the squares with a little water and sprinkle extra sea salt on top if desired. Prick each square a few times with a fork.

Transfer the parchment paper with the dough onto a baking sheet.

Immediately reduce the oven temperature to 425°F and bake for 12-17 minutes, or until the crackers start to turn golden.