Build your levain: Add active sourdough starter, 200g rye flour and 200 g water to a medium mixing bowl and whisk until well mixed. Lightly cover and leave on the counter for about 12 hours.

Check your levain for readiness: The top may not appear bubbly but should appear risen and may feel spongy & springy to the touch. The top may also have a cracked appearance, and if you're using a glass bowl, the sides and bottom should show lots of small bubbles throughout.

 If these signs aren't present leave the levain to ferment another hour and check again.

To a large bowl add the remaining 500 g rye flour and 400 g water, the salt, and the entire ripe levain. Mix very thoroughly, cover and leave to sit at a warm room temperature for 1.5-2 hours. 

At the end of bulk fermentation your dough will be moderately risen in the bowl with a cracked appearance on top and lots of little bubbles scattered throughout the bottom and sides of the bowl.

Shape your dough: You have options in terms of loaf size. If you want a few smaller loaves, this recipe can be split into five small loaves or approximately 250g each, or two large loaves of approximately 650 g each.

Either way, line a couple of baking sheets with parchment paper, and flour a clean work surface. This dough is quite sticky, and I highly recommend handling it with wet hands!

Wet your hands with a little water and scrape your dough onto your work surface. Gently shape your loaves into your desired shape and size. Some classic shapes include long rectangles, flattish rounds or "O" shapes- rounds with a hole in the center. This shape is traditional in some parts of Finland, where many loaves would be baked on the same day, then strung up by the hole in the center of the loaf to dry for later.

 Once your loaves are shaped and transferred to the prepared baking sheets, lightly dust the top of the dough with a little more rye flour- this step is optional, but your plastic wrap is basically guaranteed to stick to the top of your loaves during the second dough rise if you don't. 

Cover the loaves with plastic wrap and set in a warm place to rise for 1.5-2 hours, until the loaves look moderately puffy and risen. The flour on top of the dough will have a cracked appearance. 

Toward the end of this final proof, preheat your oven to 450 degrees Farenheit. Prick your loaves a few times with a fork before baking them.

 Bake the loaves at 450 degrees for 10 minutes, then decrease the oven temp to 400 degrees for the remainder of the cooking time. Total cook time will vary based on the size of your loaves but will be approximately 45-60 minutes.

When the loaves are done, they will sound hollow when tapped, but since it's hard to tell when 100% sourdough rye bread is done by appearance alone, I recommend double checking the internal temperature of the bread- it is done when it reaches 205 degrees Farenheit.

 Allow the loaves to cool to about room temperature, then wrap them in a clean kitchen towel and leave them on the counter for 24 hours before slicing. This waiting period is a bit painful, but it will allow the loaves to soften and crumb to set fully, so for best results definitely employ some patience and let that bread sit!