First make Levain
In a medium bowl add bread flour, whole wheat flour, rye flour, active sourdough starter and water and set aside for 6- 12 hours at room temperature.
Autolyse the flour
In a large bowl add, bread flour, whole wheat flour, rye flour, oatmeal bran and 415g water and mix and set aside for 1-2 hours.
First mix in levain into the flour mix and set aside for 30 minutes. Then add, salt, and 10g water mix everything and set aside.
Fold and stretch the dough at 30 minutes interval for 2 hours and then 1-hour interval for next 3 hours.
Make sure to do three sets of gentle stretch and folds during bulk, spaced out by 30 minutes You do not need to do any stretch and fold during rest of bulk fermentation. This is because rye does not have much gluten.
Then pre-shape the dough. In a workspace if you want you can dust lightly with flour, I usually skip this step. Transfer the dough from the bowl lightly pulling the dough towards you. This gentle turning and pulling motion will develop tension on the top of the dough forming a round circle. Let the dough rest for 25-30 minutes, uncovered.
Shape the dough
Repeat what you did in pre-shape and shape the dough into a batard . First fold the dough from left to 1/3 rd of the middle . Fold the right side of the circle out and over to about the middle, just overlapping the left side that was just folded. Using your two index fingers, or thumbs, press the top of the folded down into the rest of the dough, so it lightly seals. Continue rolling the entire mass down, sealing at each fold-over and shape into long ball.
After shaping place seam-side-up into a towel-lined kitchen bowl or banneton that was lightly dusted with rice flour and all-purpose flour.
Once you shaped the dough transfer to banneton and set aside refrigerator for cold ferment for 12 hours.
Refrigerate for overnight, next morning pre-heat oven to 450F. Transfer the dough to cold Turkey roaster and bake for 10 minutes at 450F and then reduce the temperature to 425 F and bake 25 minutes with lid on. Then remove the lid and bake for another 10 minutes or until loaf develop golden color and when you tap the loaf it makes whole sound or register 210 F internal temperature.
Cool the loaf and cut it into slice and enjoy.