Crack the rye as little as possible. Each grain must have the endosperm exposed, but otherwise be as large as possible. The boiling water is important as it gelatinizes the rye starches making them retain moisture in the final bread. I baked for only 12 hours and it was ok, but would probably be darker and sweeter at 24. Parchment should be pressed against the dough and made to seal in moisture. Foil wrapped tight.
