Combine rye flour, salt, yeast, treacle, and most of the water in a bowl.
Gradually incorporate remaining water until a soft, rough dough forms.
Knead the dough on an oiled surface for 5 to 10 minutes until a skin develops.
Shape the dough into a round cob and place into a floured proving basket.
Cover and leave to prove for eight hours or overnight until doubled in size.
Preheat the oven to 220°C and place a roasting tray in the bottom.
Half-fill the hot roasting tray with boiling water to create steam.
Invert dough onto a lined tray, slash with a crosshatch, and bake for 30 minutes.
Cool the bread significantly before slicing and serving.