Mix the dough

• In a large bowl, whisk the active sourdough starter and warm water until fully dissolved.
• Add the olive oil and salt, stir to combine.
• Add the bread flour and mix until a shaggy dough forms; the dough will be soft and sticky.

Rest and fold

• Cover the dough and rest for 30 minutes.
• Perform 1 stretch and fold, then rest for another 30 minutes.
• Do 2 coil folds, spaced 30 minutes apart, then let the dough rest for another 30 minutes.

Cold-proof overnight

• Transfer the dough, covered, to the fridge to cold-proof overnight.

Shape in the tray

• Line a baking tray with parchment paper and generously drizzle it with olive oil.
• Gently tip the dough onto the tray, fold it inwards a few times, then flip it seam-side down.
• Cover and let it proof at room temperature until noticeably puffy and spread in the tray.

Dimple and top

• Drizzle more olive oil over the surface.
• With oiled fingers, gently dimple the dough all over.
• Top with fresh rosemary and a generous sprinkle of flaky sea salt.

Bake

• Bake in a preheated oven at 230 °C until golden brown and crisp on the edges.

Cool and slice

• Allow the focaccia to cool in the tray before slicing.
• Enjoy warm or at room temperature.