Mix the dough
In a large bowl, combine flour, yeast, and salt. Add warm water and mix until a sticky, shaggy dough forms. No kneading required.

First rise
Cover the bowl and let the dough rise at room temperature for 2–3 hours, until puffy and doubled.

Prepare the pan
Generously coat a metal sheet pan or 9×13 pan with 1½–2 tablespoons olive oil.

Shape the dough
Transfer the dough to the pan. Gently stretch it toward the edges. If it resists, let it rest 10 minutes, then continue.

Dimple and oil
Drizzle remaining olive oil over the dough. Using oiled fingertips, press dimples straight down to the pan. Sprinkle with flaky salt or rosemary if using.

Bake
Bake in a fully preheated 450°F (232°C) oven on the lower-middle rack for 20–25 minutes, until deeply golden.

De-pan for crispness
Immediately lift the focaccia out of the pan and place it on a cooling rack for 3–5 minutes before slicing.