NATURALLY LEAVENED RYE AND OAT BREAD

Steps:

• Starter/Levain
• I made 200g of almost all-rye sourdough starter by feeding 40g starter with 80g water and 80g whole grain rye flour, and I used it when it was a little more than doubled in size. Other ways of building up this large amount of ripe starter are fine too.
• Mixing and Bulk Fermentation
• Combine all the ingredients in a large bowl and mix well. If possible, scrape the batter into a straight-walled dough bucket or separate out a tiny amount of dough to put in an aliquot jar to help track fermentation (explanation above, photo in the gallery below).
• Cover and let the batter rise until it has expanded by about 75%. In my ~80°F lit oven, this was about five hours.
• Shaping and Final Proof
• Grease a non-stick loaf pan or line a regular loaf pan with parchment paper. I used a medium USA pan, which is 9 x 5 x 2.75 inches.
• Scrape the batter out of your bowl or bucket directly into the loaf pan.
• Repeatedly wet a spatula with water to smooth out the surface of the batter, dipping between the edges of the batter and the pan to create the curved edges of a loaf shape.
• Sprinkle with rye flour if desired, cover, and let the batter rise about 2 centimeters. (See the gallery below for a sense of the expansion.)
• Baking
• Preheat your oven to 450°F for about 20 minutes with a pan on the bottom shelf. You'll pour boiling water into the hot pan when you load the bread into the oven. An alternate option for steam is to make a tight foil tent around the loaf pan and leave it on for the first 15-20 minutes of the bake.
• Boil a cup of water.
• Place the loaf pan in the oven and pour the boiled water on the hot pan below it, then quickly close the oven door.
• Bake for 20 minutes, then lower the oven temperature to 390°F, and bake another 25-30 minutes. Rotate the pan if needed for even browning. The internal temperature of the bread should be over 208°F when it's done.
• If possible, wait 24 hours before cutting the bread to let the inside set. You might want to rotate the loaf onto one long side and then the other during this setting period, so it doesn't get dense at the base. If you can't wait for the loaf to set, toast each slice to solidify the crumb.