Pour in the vegetable stock. Bring to a boil over high heat, then lower heat to medium-low, cover, and cook until the potatoes have softened, about 15 minutes. Stir the flour into the sour cream, and add it a spoonful at a time to the simmering soup. Stir in the sauerkraut and dill, season to taste with salt and pepper. Simmer for 5 minutes more before serving.