Using a digital scale set to metric, measure 90 g rye sourdough starter into a minimum 4 liter food grade container or large bowl. (In photos, I use a 6 L Rubbermaid food bin with lid).
Using a scale, measure 315 g warm (not hot) water. Add water to starter. Mix well to break up the starter and create a milky slurry.
Using a scale, measure 45 g of thick rolled oats. Add to slurry and mix to combine.
Using a scale, measure 90 g whole wheat flour.
Using a scale measure 270 g bread flour and mix together with whole wheat flour.
Mix flours together with slurry/oatmeal until there are no dry bits remaining.
Cover container tightly, set aside, rest for 30-35 minutes so flour will autolyze.
Using a scale, measure 11 grams of sea salt. Sprinkle sea salt over the autolyzed flour and water mixture.
Grab outside of the dough and pull towards center about 4-6 times to cover the salt.
Cut through the mixture three times by squeezing two fingertips together (like you are forming the “okay” symbol). Next, grab a small portion of dough from one side and pull dough up, then fold the dough down over itself 4- 6 times. Be careful not to pull too much as dough will tear. Rotate the container a quarter turn and repeat. Do this a total of four times. After the final fold flip the dough over so folds are tucked below dough mass.
Replace the cover and allow dough mixture to rest for 10 minutes.