Mix 1/3 cup water and 1/2 teaspoon of yeast, let rest for 10 minutes. Add 2/3 cup flour and mix until smooth, about two minutes. This is the biga, or starter. Put it in a bowl and let it sit in a cool oven for one hour, then transfer to refrigerator overnight.
Take the biga out of the fridge and let it come to room temp – about 30 minutes. Add to bowl and add 1 1/3 cup water, 1 teaspoon yeast and stir until the biga starts to dissolve a bit. Add in the remaining 3 1/4 cups flour with oil and salt. Just mix until the flour is incorporated, let rest 20 minutes. This step apparently hydrates the flour.
Knead the dough on your counter, adding just enough flour so it doesn’t stick to your hands or the counter. Knead for 10 minutes. Transfer the dough to a bowl with olive oil and let rise for two hours.
After two hours, divide the dough into two loaves. Let rest for another hour. Bake at 425 on a baking stone for 30-40 minutes, adding ice cubes to a cast iron skillet. Bake loaves until dark golden brown and crisp; let cool before serving.