For the sourdough, mix 100 g rye flour with 100 g water and leave in a warm place for 48 hours. Cover it well, but do not close it airtight if possible.
After the 2 days add another 100 g flour and 100 g water. Mix again and let stand for another 24 hours.
Then add the remaining 200 g flour and 200 g water and let stand for another 24 hours.
For the bread, mix the specified ingredients for the main dough with 700 g of the finished sourdough. (Put the remaining sourdough in a screw-top jar or a plastic jar with a lid. You will need it for the next bread.) Knead well and let rise for another hour.
Then knead again and form a loaf of bread (two smaller ones if you like). Let rise for about 30 minutes and then bake in a preheated oven at 200 ° C top / bottom heat for about 70 - 80 minutes.
To make the crust nice and crispy, brush the bread several times with cold water during the baking process.
Note: The leftover sourdough can be stored in the refrigerator for 1 to 2 weeks. To bake a new bread, just add 350 g of rye flour and 350 g of water. This sourdough is ready after 24 hours.