Start by feeding your starter. Mix together starter, water, and flour. Allow it to sit for at least 1 hour until bubbles surface evenly across your fed starter.
Stir in the ingredients for your bread dough: flour, yeast, olive oil, salt, and sugar. Stir until everything is well incorporated. Cover and rest for 1 hour in a warm spot.
Turn your dough out onto a well-floured surface. Using a bench scraper, stretch and pull all four sides of the dough into the center. Repeat stretching and pulling all four sides a second, third, and fourth time.
Flip the dough over and roll it between your hands, rotating it in a circle to seal the bottom and tighten the skin on top.
Lay a towel into a colander or line your sourdough bread basket. Flour the fabric liberally. Set your dough into the basket top side down (the seam facing up). Flour the seam-side of the dough and cover with a towel. Let it rise for 1 to 2 hours (until doubled in size) in a warm spot.
Preheat the oven to 400ºF for 1 hour.
Meanwhile, crumble up a sheet of parchment paper and form it into a cast iron pan. Dust with flour.
Turn your dough out into the lined cast iron pan. Score the top. Rest for 1 hour while the oven preheats.
Place your cast iron in the oven and bake for 40 minutes.
Allow your bread to cool completely before cutting into it.