Add the ingredients for the starter to a large bowl and mix together until smooth. Set aside for 10 minutes for the yeast to activate.
While the starter is resting, mix together the flour mixture – bread flour, caraway seed, salt and instant yeast.
Pour the flour mixture over the starter but do not stir. Cover the bowl with plastic wrap or a clean towel and set aside for at least two hours and up to five hours.
The starter will bubble up a bit through the flour mixture. This long rest will give your loaf a boost of flavor.
Add the oil to the flour mixture and use a wooden spoon to stir the flour mixture into the starter. As the mixture comes together, remove the dough to a lightly floured work surface and knead for about 10 minutes, or until smooth and elastic. The dough might be a little sticky. Knead in just enough extra flour to keep the dough from sticking to your hands.
Set the dough aside to rest for about 10 minutes, then knead for another 5 to 10 minutes.
Set the dough in a large, lightly oiled bowl and lightly oil the top of the dough. Cover with plastic wrap or a clean towel and set in a draft-free area of the kitchen to rise until doubled in size, about 1 1/2 to 2 hours. Remove the dough to a lightly floured work surface. Punch down the dough and lightly knead it 3 or 4 times. Form into a ball, return to the bowl, cover and let rise for another 45 minutes or so.
Preheat oven to 425°F and set the shelf at the lowest level. Put a small metal pan in the oven (you will use this later). Lightly press down on the dough and form it into a ball. Sprinkle the cornmeal onto a baking sheet and set the dough onto the baking sheet, with any seams on the bottom. Lightly oil the top of the dough and cover it with plastic wrap. Set aside to rise for another hour.
Use a sharp knife or razor blade to slash the top of the dough in 3 parallel lines, each about 1/4-inch deep. Then slash with another set of 3 lines perpendicular to the first set. Use a spray bottle to mist the dough with water.
Set the baking sheet in the oven and pour about 1 cup of water into the small pan to create steam. Shut the door immediately and bake for 15 minutes. Reduce heat to 400°F and bake for another 35 to 45 minutes. (An insta-read thermometer inserted into the middle of the loaf should register 190°F.)
Set the loaf on a cooling rack and let cool.