Combine active starter, room temperature water, flour, and oil in stand mixer and mix until combined.
Allow to sit for 20 minutes then add the salt and mix until combined.
Put dough in a non-metal bowl, cover, and sit at room temperature for 6 hours.
After the 6 hours, remove the dough onto a work surface and separate into two halves. Form each half into a tight ball and allow to sit undisturbed for 10 minutes. Flour the banneton baskets.
Gently place each ball of dough into a basket upside down. Cover and allow to sit for 2 hours.
After 2 hours, preheat oven to 450 degrees with dutch oven in it for 30 minutes.
Place one ball of dough onto a piece of parchment paper and score using a sharp knife or bread lame.
Carefully remove the dutch oven lid, place the dough on the parchment into the dutch oven, replace the lid, and close the oven door. Bake for 20 minutes.
After 20 minutes, remove the dutch oven lid from the oven and decrease the oven temperature to 425 degrees F.
Bake for another 15 minutes or until the loaf is lightly browned and has an internal temperature of 200 degrees F. Allow to cool on a wire rack.
Increase oven temperature back to 450 degrees F and put the lid back on the dutch oven. Repeat instructions for second loaf.