Mix warm water with flour and sourdough starter, and leave the pre-dough to ferment for 8-10 hours. When the bubbling has subsided, add the remaining flour, sugar, and salt. The amount of flour may vary slightly depending on room humidity, etc. Mix the dough thoroughly with a wooden spoon. Take about 1 dl of dough and store it in a lidded container in the fridge for your next bread-making. Add the remaining dough with caraway seeds (for a more intense flavor, you can lightly crush them) and beat with a wooden spoon for about five minutes, until the dough becomes slightly lighter in color. 

Grease a 35-cm long baking tin with butter or line it with baking paper. Transfer the dough into the tin, smooth the surface evenly with a wet hand. If desired, press three holes into the dough, make a cross or a family mark to make it easier to monitor the rising process, cover with a towel, and let it rise in a warm place for about one to one and a half hours. 

Once the dough has risen sufficiently, place the tin in a preheated oven at 200 degrees and bake for one hour. Turn off the oven and let it stand inside for another 5 minutes. Remove the tin from the oven, run a wet hand over the surface of the bread, and cover with a damp kitchen towel for 5 minutes. Turn the loaf out of the tin and wrap it in a damp towel until it has completely cooled.