Measurements are in weight and grams here because that is what helps me achieve consistent results every time. I'm simply not a good enough bread baker to "wing it" with volumetric measurements, which can vary widely depending on the person.
Mix the rye flour, rye starter and water together in a bowl by hand until it looks like wet clay. Cover and let sit out on the counter 8 to 10 hours. Do this in the morning.
That evening, put the covered bowl in the fridge. This is optional, but makes a better bread.
The next morning, first thing, take the sponge out of the fridge to come to room temperature for an hour or more.
Add the sponge, bread flour and warm water to the bowl of a mixer and mix with the paddle on its slowest setting for 3 minutes. Scrape down the paddle, cover the bowl and let this sit 15 minutes.
Sprinkle the salt and yeast on the mixture, then use the dough hook to mix it all for 30 minutes, again at the slowest setting. This process develops the gluten so the loaf can hold large air pockets later. Use a rubber spatula to scrape down the sides of the bowl to form a roudish ball. (See photo above) Cover the bowl and let this ferment 2 hours, up to 2.5 hours in cold weather. The dough should double in size.
With about 30 minutes to go in the ferment, put a rack in the middle of the oven, and preheat it to 450°F. Boil some water and put it in an oven-proof container, like a hotel pan, in the oven.
When the dough is ready, use a rubber spatula to scrape it out of the bowl carefully, keeping as much air in the dough as possible, and onto a well-floured surface. Using floured hands, roughly shape it into a ball by folding the corners in on themselves. Carefully move the very gooshy dough into a banneton. Cover it with a linen cloth or somesuch and let this proof 10 minutes.
Line a baking sheet with parchment paper. When the oven is ready, flip the dough from the banneton to the parchment paper and into the oven. Do this quickly. Bake the bread with the steam tray for 15 minutes.
Remove the tray and drop the heat to 390°F. Bake until the loaf is golden brown and thumps when you tap it on the bottom, about 30 to 35 more minutes. Don't slice it until the loaf has fully cooled.