Prepare the Biga Stir together flour, water, and yeast in a small bowl, forming a sticky dough. Cover bowl tightly with plastic wrap, and refrigerate for at least 12 hours or up to 24 hours. (Biga will rise slightly.)

Prepare the Bread Place Biga, oil, sugar, yeast, salt, and 1 cup of the water in the bowl of a stand mixer fitted with a paddle attachment. Beat on low speed until mixture looks creamy, about 1 minute. Add flour, beating on low speed. Increase mixer speed to medium, and beat until dough starts to pull away from sides of the bowl, about 2 minutes. Switch to a dough hook attachment, and beat on medium speed until smooth and elastic, about 8 minutes. Transfer dough to a large greased bowl, and cover with plastic wrap. Let stand in a warm place until almost doubled in size, about 2 hours.

Stir together baking soda and remaining 1 tablespoon water in a small bowl until combined. Punch dough down, and stir in baking soda mixture until combined (it will be streaky).

Brush an 8 ½- x 4 ½-inch loaf pan with 1 tablespoon of the melted butter. Transfer dough to prepared loaf pan, and cover with greased plastic wrap. Let stand in a warm place until almost doubled in size, about 1 hour.

Preheat oven to 375°F. Uncover dough, and brush with remaining 1 tablespoon melted butter, and sprinkle with cornmeal. Bake in preheated oven until golden brown, about 30 minutes. Let cool in loaf pan 5 minutes; invert onto a wire rack, and brush with any remaining butter. Let cool completely, about 1 hour.