For the best results, heat the oven to 240C/fan 220C/gas 9 with a round casserole inside. Dust the loaf with a shake of rye flour, if you like, and slash a few times with a sharp knife. Use the paper to lift it into the heated dish, then bake for 20 minutes with the lid on. Remove the lid and bake for 20 minutes more until the loaf has browned and sounds hollow when tapped. Alternatively, heat a tray in the oven to 220C/fan 200C/gas 7 then dust, slash and bake the loaf for 30-40 minutes or until browned and sounding hollow when tapped. Cool completely before slicing.