Combine flour, yeast, salt, and water in a bowl until everything is well incorporated.

Cover and let rise in the fridge overnight (at least 12-18 hours).

Oil a baking dish well and transfer dough (which should have doubled in size), spreading gently to edges.

Cover and let rise at room temperature for an additional 2-4 hours. The dough should now be plump and jiggly.

Preheat oven to 210 degrees Celcius.

Drizzle olive oil liberally over the top of your dough and dimple gently with your fingertips. Sprinkle with rosemary and flaky salt.

Bake for 30 minutes or until the top is golden brown.