Use 120 g inactive sourdough starter and feed it in a 1:1:1 ratio:120 g inactive starter (= ⅓ cup)120 g lukewarm water (= ½ cup)120 g unbleached flour, whole wheat (= ¾ cup)Combine starter with water, then add flour.Let it rest for 6-10 hours.
Prepare dough
Combine 225 g active sourdough starter with the water until milky using a silicone spatula.
Gently add in the flour, salt and if using, the olive oil.
Use the silicone spatula to combine until even.
Bunch up the parchment paper and make it wet. Place it in the bread pan.
Now add the dough and spread it evenly.
Cut a long line from left to right (about ½ inch deep).
Let dough rest
Cover with a moist (not wet) cotton or paper towel.
Let the dough rest 4-10 hours.
Prepare for baking
With a baking brush add water to the top. Sprinkle "everything but the bagel spice" and the oat flakes on top.
Cover with aluminum foil.
Baking
Place an oven safe cup or pan with a cup of water in with the bread while baking.
Bake at 425℉ (220℃) for 1 hour. Keep covered for the first 45 minutes.
Let cool
Let bread cool on rack for at least 2-3 hours before cutting into it. (Unless you are planning to eat the whole bread in one sitting). Once the bread is cut into it loses moisture as it still evaporates.
Enjoy
Enjoy simply with some (vegan) butter and cheese with lettuce. Let the bread speak for itself.