Night before focaccia mixing: stir together the 60 grams each all-purpose flour and water and 6 grams active 100%-hyrdration starter in a half-pint jar. Cover loosely and allow to develop at room temperature for at least 8 hours—jar will become filled.

Mix together the starter (or levain), flours, salt, and 450 grams water in a stand mixer using a dough hook. Mix with dough hook until dough stretches from the side of the bowl and gathers around the hook, 5 minutes. Let dough rest for 10 minutes, bowl covered.

Turn the mixer back on a low speed and add additional 25 grams water (perhaps more) to make a well-hydrated dough. Slowly drizzle in the olive oil. Once incorporated, increase speed and mix for a couple minutes. Focaccia dough is meant to be slack but will come together more during fermentation.

Begin 2 hours fermentation with stretch-and-folds every 30 minutes.

Liberally coat pan(s) with olive oil, about ¼ cup for the sheet pan or rectangular cake pan, 2 tablespoons each for rounds. Scoop dough into pans and with wet fingers, press out a bit; dough will relax and fill the pan better over time. Cover and allow to proof in a warm spot.

During the first 2 hours, uncover every 30 minutes and using wet fingers, gently poke and push the dough towards the pan edge. For the remainder of the proofing, allow the focaccia to sit undisturbed so it can become puffed and bubbly.

To delay the bake until next day, place covered pan in refrigerator after first 2 hours of proofing. Next day, remove from refrigerator, and allow to proof at room temperature until bubbly.

Preheat oven to 425°F. At the end of proofing, use wet fingers to press to the bottom of the pan. Drizzle surface with remaining olive oil, sprinkle with pretzel salt or coarse salt, and optionally decorate top with toppings of your choice—slivered dried tomatoes, olives, sprigs of rosemary, etc.

Bake focaccia for 30 minutes, until top is golden brown.(Round pans will take less time, check at 25 minutes.)