Into a big mixing bowl add in 100 grams of the bubbly pre dough and 400 grams room temperature water, stir to combine.
Add in 500 grams bread flour.
Use your hand to stir and knead the dough until all of the flour has been hydrated aka no dry bits remain.
Cover the bowl with plastic or a lid and leave it to sit for 20 minutes.
After 20 minutes, uncover and add in 25 grams more water and 10 grams fine sea salt. Knead again squishing the dough between your fingers. First it will break apart but it will start to come back together. It doesn't need to be smooth at all just a cohesive dough. Recover and leave to sit out on the counter for 45 minutes.
After 45 minutes it's time to start stretching and folding the dough. Wet your hands, and scoop under the dough and lift from the center, stretching the dough up. Keep pulling until all the dough has lifted from the bowl, then gently lay it back down.
Turn the bowl 90 degrees and repeat scooping under, pulling, and lifting the dough, then lay it back down.
Cover the bowl again and leave to sit for 45 more minutes.
Stretch and pull 3 more times always leaving it to rest for 45 minutes in between. *If your room or home is above 72 degrees, you can cut the time down to 30 minutes.
After the last stretch and pull, cover the bowl tightly and place it in the fridge overnight.