Measure and sift flour and cocoa powder into a large bowl
Measure and add starter, water, and maple syrup into a separate bowl and mix
When the starter has mostly dissolved into the water, pour flour mixture into the bowl
Stir until the mixture forms a very rough dough
Cover and rest for 30 minutes (this is the autolyse)
Add your salt to the dough and use your hands or dough hook attachment to incorporate all the ingredients by kneading
Once the salt is distributed, cover your dough with a lid, moist towel or clean shower cap
For the next hour, stretch and fold your dough every 15 minutes
For two hours after that, stretch and fold your dough every 30 minutes
After the stretch and folds are done, cover and allow to bulk ferment for 4 hours or until doubled in size
Turn out the dough onto a clean work surface and pre-shape into a large ball. Rest for 15-20 minutes
Tightly share the loaf and transfer into a floured banneton or colander lined with a floured tea towel
Cover and place in the fridge for 8-10 hours