- Combine the ingredients of fluid starter in a large mixing bowl. Cover with a plastic wrap and set aisde for 12-16 hours at room temperature. In the bowl of a stand mixer, mix the fluid starter, water and spelt flour, and rye flour on low speed until just combined, about 1 minute. Let the dough rest for 30 minutes. Scatter in the salt and continue mixing on low speed until the dough reaches a medium level of gluten development. This should only take about 3 or 4 minutes.
- Transfer the dough to an oiled container. Ferment at room temperature for 2.5 hours, with folds at 50 and 100 minutes. Turn the dough out onto a lightly floured counter. Divide it into two portions. Preshape the dough pieces into balls. Sprinkle the balls lightly with flour, cover loosely with plastic, and let rest for 15 minutes.
- Shape them into batards or boules and place seam-side-up in a floured proofing baskets. Proof the dough, covered with plastic wrap, at room temperature for 2.5 hours. Alternatively, the loaves can be proofed for about 100 minutes at room temperature, then refrigerated for 2 – 16 hours and baked directly out of the refrigerator.
- An hour before baking, start preheating the oven together with baking stone and a roasting pan on the bottom of the oven to 220C/450F. Turn out the loaves onto a baking shovel or the back of a baking sheet sprinkled with semolina. Slash the loaves as your like.
- Once the oven reaches the temperatures, place in the bread dough and fill the heated roasting pan with 1/2-inch of hot water. Immediately close the oven and bake for 40 minutes. Cool on a wire rack.