A sourdough focaccia that's crispy on the outside, spongy on the inside, and flavored with whatever you want! This focaccia is even easier than your standard sourdough loaf, and it gets so much flavor from the long rise.
Combine the water and starter in a large bowl until combined (it's okay if there are some lumps of starter at this point). Add the flour and salt and stir until fully combined. Cover and let the dough rest for 30 minutes - 1 hour, then do a round of stretch and folds. Cover and let rise at room temperature for 6-8 hours, until doubled in size.Once the dough has doubled, prepare a 9 by 13-inch metal baking pan (see note) by coating with 3 tablespoons of the olive oil. Spread it around the bottom and sides of the pan with your fingertips. Turn the risen dough out into the pan with oiled fingertips, flatten into a rectangle using your fingertips, then fold it like an envelope to make a neater rectangle. Flip the dough over so the seams are facing down. Cover and let rise for 4-6 hours more, until nearly doubled again. Preheat oven to 425 degrees. Drizzle the remaining 1 tablespoon olive oil over the dough, rubbing some on your fingertips too. Press all fingertips into the dough to dimple and stretch to fill the pan. It's okay if it doesn't fully stretch into the corners! Whatever you do, DO NOT pop any air bubbles at this stage - they are delightful in focaccia. Top with the salt and any additional toppings you're using, and bake for 25-30 minutes, until golden and bubbly.Remove from the pan immediately, and allow to cool slightly on a metal rack before slicing.
Notes
The pan - I've had had issues with focaccia sticking to the pan in the past. I have never had any problem with the USA pan listed in the post and below. If you have any doubts about whether your pan will cause sticking, I highly recommend lining it with parchment paper.