Feed your starter: Make sure your starter is active and bubbly. It should double in size within 4–6 hours of feeding. Use it at peak or just before it starts to fall.

Mix the dough (autolyse): In a large bowl, combine the flour and 350 g of the water until no dry bits remain. Cover and rest for 30–45 minutes. This jumpstarts gluten development.

Add starter and salt: Add the active starter and 10–12 g salt. Mix by hand or with a dough hook on low until cohesive. If the dough feels stiff, add the remaining water a little at a time. The dough should be soft and slightly sticky.

Bulk fermentation with folds: Drizzle a little olive oil into the bowl. Over the next 2–3 hours at room temperature (around 72°F/22°C), perform 3–4 sets of stretch-and-folds every 30 minutes. To do this, wet your hand, grab one edge of the dough, stretch it up, and fold it over itself. Rotate the bowl and repeat 3–4 times per set.

Let it rise: After the last fold, cover and let the dough rise until puffy and roughly doubled. This can take 3–5 more hours depending on temperature and starter strength. Look for bubbles and a light, jiggly feel.

Pan prep: Generously oil a rimmed sheet pan (about 9x13 inches for thicker focaccia, or a larger sheet for thinner). Add 2–3 tablespoons olive oil to coat the bottom well.

First pan proof: Gently turn the dough into the pan. Drizzle the top with olive oil. With oiled fingertips, carefully press and coax the dough toward the corners. Don’t force it; if it springs back, rest 15 minutes and try again.

Second rise: Cover and let the dough relax and puff for 45–90 minutes at room temp, or refrigerate overnight (8–16 hours) for deeper flavor. If chilled, let it warm 45–60 minutes before baking.

Dimple and top: Heat oven to 450°F (232°C). With oiled hands, press your fingertips straight down into the dough to create deep dimples. Scatter rosemary, garlic, tomatoes, or olives if using. Finish with a generous drizzle of olive oil and a sprinkle of flaky salt.

Bake: Bake 20–28 minutes until deeply golden, with crisp edges. Rotate the pan once for even color. For extra bottom crunch, bake on a preheated baking steel or the lowest rack.

Finish and rest: Remove from the oven and brush or drizzle with a little more olive oil. Let cool in the pan 10 minutes, then transfer to a rack. Rest another 10–15 minutes before slicing to keep the crumb moist.