Your leaven should now look bubbly, pinch off a little and place into a bowl of water. If it floats, it is ready to be used. If it's not floating, let it rest some more, check back in 1-2hrs
In a large mixing bowl, weigh out 100g leaven and 325g water. Mix together well. Add in the flours and and mix together with your hand until a shaggy dough forms. It's fine if it feels quite dry. Cover with a tea towel or shower cap and let rest ad hydrate for 30mins.
Add the salt and 50g of water to the dough. Mix together well, the dough will still feel a bit dry but should feel more homogenous. If it's really dry you can add another 20g of water, but keep in mind it will continue to hydrate over the next few hours and become wetter, so at this stage a drier dough is fine.
Sprinkle in your flavours if desired, my go to is pepitas and rosemary fronds. Make sure these are mixed well throughout the dough as well. Cover the bowl with a tea towel or shower cap and let it rest for 30mins.
After 30mins, it's time to do your first fold. Wet your hands and starting from the side away from you, grab the dough and pull up as much as you can then fold it towards you. Turn the bowl 90 degrees clockwise and repeat. Keep repeating until you have done a full circle around the bowl. You have finished one fold. Cover and let rest for another 30mins.
After 30 mins, repeat the folding process and let the dough rest again for another 30mins. You want to repeat this process for 4-6 times. After the last fold, let the dough rest, covered for another 30mins.