In a mixing bowl combine flour and water making sure there are no clumps. Then press the cranberries evenly into the wet mix cover with a lightly wet tea towel and keep in a warm place for 24 hours.
Remove cranberries along with 90% of the mix before replacing with 100 grams of fresh flour flour and 100 grams water, cover with lightly wet tea towel and keep in a warm place for 24 hours.
Repeat step 2, (this is re-feeding, providing the microbes with fresh food to thrive and grow).
By now you might see some bubbles on the surface of your mix and a funky smell this is a good sign and typically it is ready for use, but I always like to go an extra day. If you are yet to experience this keep going until you do.
This next day you are ready to transfer your dough to an airtight container and keep it in the pantry. Be sure to remove a portion every day either for use in a sourdough or to re-feed.
Factor to consider.
-The Cranberries contain natural sugars for the bacteria to initially feed off and begin to grow, you can do it without, but I like the little boost they can give.
-You are growing bacteria which means they develop more efficiently in warmer temperatures, hence the reason for leaving in the warmer locations overnight.