Mix the ingredients for the sourdough, cover with cling film and let stand for 16-20 hours at room temperature. Then add all the ingredients and slowly knead with the food processor for 10 minutes. Cover and let the dough rest for 30 minutes.
Knead again thoroughly and pour into a greased loaf tin sprinkled with oat flakes. Brush with water and sprinkle with spelled flakes. Cover and let rise in a warm place for 1.5 hours. Bake in the preheated oven at 250 ° top / bottom heat on the second shelf from the bottom for 10 minutes, turn the stove down to 200 ° and bake for another 40 minutes (if necessary, do a tapping test).