Spread oatmeal on a baking tray and roast them in the upper part of the oven in 480ºF / 250ºC until lightly browned. Let the oatmeal cool.

Mix all ingredients except the salt. Make sure that all flour is hydrated. Let the dough rest for an hour. You can also let the dough autolyze for an hour. In that case, mix the starter together with the salt afterward.

Add the salt and perform one stretch and fold. Perform 3 additional sets of stretch and folds during bulk fermentation, spaced out by 30 minutes.

Let the dough rest for about 4-5 hours at a temperature of 78ºF/25ºC if possible.

Lightly flour your work surface and dump out the dough. Flatten the dough gently with your hands. Form each piece of dough to a boule. There's a link to an excellent video showing how to form a boule in the recipe notes*. Spread linseed together with some flour into the banneton before adding the dough.

Let the loaves rise until they pass the finger poke test. The time required depends a lot on ambient temperature so don't look at the clock.

Preheat your oven to 480ºF / 250ºC with two oven plates. One to bake the bread on and one just below. If you have a baking stone or dutch oven, use them instead.

Score the loaves in your preferred pattern and place them in the oven. Pour some water on the plate below and bake each loaf in 30-40 minutes.

Let the breads cool on wire racks.