Knead the water and flour for about 1 minute so that the dough coarsely comes together. Then let the dough rest for 20-30 minutes.
Then add the yeast, salt and wheat sourdough and knead until the dough separates from the bowl.
Put the dough in a bowl and let rise for 90 minutes. Fold every 30 minutes.
Then place the dough on a floured worktop, divide it into 2 halves and roughly shape into balls. Let rest for another 15 minutes.
Shape the dough pieces into oval loaves and press deeply in the middle with a thin rolling pin. Roll the rolling pin back and forth so that there is a gap of 5 cm. Flour this lightly and place the dough upside down in a cooking basket or between a cloth and cover. Let rise for 2 - 2 1/2 hours.