Start by mixing 50 g of flour with 50 g of water. Mix it well together and leave it in a semi-open container, at room temperature. I usually perforate a sheet of plastic, that I use to cover the mix with.

Throw out all of the yesterday's dough except one tablespoon. mix that tablespoon of dough with another 50 g of flour and 50 of water.

At the end of day 6, you should have noticed that there are small pockets of air in the mix. If there is not you should probably throw out the mix and start over. When you spot the baubles you are ready to start preparing for baking.