Combine the warm water and starter and whisk together using a whisk, dough whisk, or fork.
325 g water, room temp or slightly warm, 100 g active sourdough starter
Add in the all-purpose flour and whole wheat flour. DO NOT add the salt just yet. Mix in the flour until everything comes together and creates a shaggy dough. I like to use my rubber bowl scraper for this step.
450 g all purpose flour, 50 g whole wheat flour
Cover with a plate or damp tea towel and let rest for an hour. This process is called fermentolyse. Salt slows down the fermentation process, so leaving it out at the beginning and letting your dough rest for an hour gives your bulk fermentation a head start.
After an hour, add half of the salt to the dough and mix it in using your hands. Add the rest of the salt and perform a few stretch and folds until the salt is completely mixed in and you don't feel any granules. If needed, sprinkle a little bit of water to help the salt dissolve. To perform a stretch and fold, grab one edge of the dough, and stretch by lifting it up and folding it to the center. Turn the bowl about a quarter turn and repeat by grabbing the edge, lifting it up, and folding it to the center. Repeat this two more times, equalling one round of stretch and folds. Perform as many as needed to mix in the salt.
10 g sea salt
Cover the bowl and let rest for 30 minutes. After 30 minutes, wet your hands and perform four stretch and folds(one round). Cover the bowl and let rest for another 30 minutes. Repeat this process three more times, equalling five rounds of stretch and folds(also counting for when we mixed in the salt).