This is a rustic bread with big, airy holes in it. It’s meant to be a wet, sloppy dough, so don’t worry if it looks a little crooked-looking by the time it ends up going into the oven. It’ll all work out and taste great in the end.
For starter, mix yeast and water to dissolve. Mix in flour by hand and stir just until blended (no lumps). Mixture will be very wet and sticky. Cover and refrigerate for at least 12 hours.
For bread dough, stir yeast and milk and mix in the bottom of the bowl of a standup mixer fitted with the paddle attachment. Add yeast, water, oil, starter and mix with the paddle until blended (or dough can be mixed by hand in a bowl with a wooden spoon). Switch to the dough hook and add flour and salt in, kneading on low speed for 2 minutes, then increasing to next speed up, kneading for 3 minutes. Slap the dough with your hand in the bowl, until it feels stretchy and springs back (it will be too sticky to knead on a work surface). Place dough into an oiled bowl, cover bowl with plastic and set in a draft-free, warm area to rise for about 90 minutes. The dough should have lots of big air bubbles visible when ready.
Turn dough out onto a lightly floured work surface and roll up into a cylinder (like you would for a loaf or bread), but then stretch and pull the flexible dough into a rectangle about 20 inches by 8 inches. Cut dough in half (so that each piece is about 10-x-4-inches) and place each on 2 parchment-lined baking trays sprinkled with cornmeal. Cover loaves gently with a slightly damp tea towel and let rise another 90 minutes.
Preheat oven to 425 °F and place a baking tray upside down in oven to heat. Remove hot tray from oven, and slide parchment with bread onto hot tray and return to oven quickly. Spray tops of loaves with a little water, close oven quickly and bake for 20 to 25 minutes, spraying again with water after 10 minutes. Remove bread from tray to cool before tearing or slicing.