In a large bowl combine the water and starter. Mix well.
Add 3 cups flour and the salt. Mix well.
If dough is too sticky, add up to 1/2 cup more flour.
Cover with plastic wrap and let dough rest for 30 minutes.
After 30 minutes, start doing stretch and folds.
To do a stretch and fold, pull up and over on a corner of the dough. Continue all the way around the bowl.
Every 30 minutes do a set of stretch and folds covering the bowl in between. You want to do at least 3 or up to 6.
In a small bowl, combine the grains.
On the 3rd set of stretch and folds, add 1 tbsp of grains before folding the dough until all grains are used.
Continue stretching and folding until the grains are evenly distributed throughout the dough.
Cover and let rise for 4-6 hours.
To shape the dough, turn it onto a work surface and much like stretching and folding, pull a corner up and over the dough all the way around.
Turn the dough over and drag across the table to build surface tension.
Place shaped dough seam side up in a banneton basket that is lined with a tea towel that is generously sprinkled with flour.
Cover and place in the fridge until ready to bake. You can leave the dough in the fridge for several days. It will continue to ferment very slowly.
Alternatively, you can finish the second rise on the counter, covered for 1-2 hours.
Preheat a dutch oven in the oven to 450 degrees F.
Turn the dough onto a piece of parchment paper.
Score the top with a sharp knife or lame.
Carefully take the dutch oven out of the oven and lower the loaf in.
Cover and let bake for 20 minutes.
Uncover and continue to bake for 15 minutes until deeply golden brown.
Let cool on a cooling rack completely before slicing.