Mix the dry ingredients in a stand mixer. Add the sourdough starter and vegetable oil. Add water or flour as needed, based on the hydration of your starter (I don't need to add either but that's likely unique to my starter hydration level).
Switch to a dough hook and knead in the stand mixer for 7 minutes. Transfer to a greased bowl and allow to rise (double in size). I use a bread proofer at 84°F and allow to rise for two hours.
After the first rise, transfer back to the stand mixer and, with the dough hook, knead three more minutes. Transfer back into the greased bowl (I sprinkle a combination of white and wheat flour on the bowl before transferring) and rise one more time to double in size (again, for me, two hours in the proofer at 84°F).
Place a cast iron dutch oven, with lid, in the oven and preheat the oven to 450°F for one hour.
Transfer the dough to the cast iron dutch oven (I place it on parchment paper). Mist with water before covering and baking for 20 minutes. After 20 minutes remove the cover of the dutch oven and bake for 10 minutes. After 10 minutes check the internal temperature of the bread with a digital thermometer. You are looking for 190 to 200°F. Continue baking until that temperature range has been reached.
Allow the bread to cool on a baking rack for two hours before slicing.