Combine flour, water, salt, and ripe sourdough starter to a large mixing bowl with the dough hook attachment.

Mix on low speed 1 for 1-2 minutes until incorporated.

Mix on medium speed 2 for 5 minutes until the dough strengthens and clumps around the hook.

Let the dough rest for about 10 minutes in the mixing bowl.

Slowly drizzle one tablespoon of the oil with the mixer on speed 1 (slow).

When the oil is absorbed, mix on speed 2 for another 1-2 minutes until the dough comes back together.

Place the dough in a bulk fermentation container and cover for 2 hours.

Stretch and fold the dough four times during bulk fermentation, with one set every 30 minutes, beginning the first set 30 minutes after the bulk fermentation starts.

Apply oil generously to the inside of a 9x13" rectangular pan.

Transfer the dough from the bulk fermentation into the rectangular pan by gently scraping it directly or placing it onto a work surface first. The dough will rise in the pan for 4 hours.

During the first hour, uncover the pan every 30 minutes, gently stretch the dough with damp hands to the baking pan's edges to help it spread, and then cover it again. Since the dough will naturally expand during this time, there's no need to stretch it excessively.

Once the dough is mostly spread, let it continue proofing for the remaining 3 hours. About 30 minutes before the proofing time ends, turn the oven on to 450°F.

Once the oven is preheated, poke the dough's surface with wet or oiled fingers.

Drizzle the remaining oil on the dough, followed by coarse sea salt.

Bake for 30 minutes or until golden brown.

Add everything bagel seasoning or whatever seasoning you desire after 20 minutes of baking. If you use fresh herbs, add them before baking.

Let the focaccia cool in the pan before moving it to a cooling rack.