How do I make sourdough focaccia?

A wet dough and a long cold rise do most of the work here:

Ingredients:

• 420 g strong white flour
• 340 g water, slightly warm
• 110 g ripe starter (fed 6–8 hours earlier)
• Finishing: olive oil, flaky salt, rosemary, thin lemon

Instructions:

1. 1.Whisk the starter into the water until it clouds and loosens.
2. 2.Add the flour and mix to a shaggy mass, then rest 40 minutes.
3. 3.Work in 9 g salt and a splash more water with wet hands.
4. 4.Fold the dough over itself four times, 30 minutes apart.
5. 5.Oil a deep tray generously and tip the dough in without deflating it.
6. 6.Cover and refrigerate overnight, 12 to 16 hours.
7. 7.Let the tray come back to room temperature before shaping.
8. 8.Dimple to the base of the tray with oiled fingertips.
9. 9.Bake at 240°C for 22 minutes, until the edges go amber.
10. 10.Brush with oil, scatter salt, and cool on a rack for 15 minutes.