Step 1
Stir 1 cup warm water 1/2 cup all-purpose flour 1/2 cup whole wheat flour 1/4 cup rye flour and yeast together in a large bowl. Cover the bowl with plastic wrap and let sit until the sponge bubbles and doubles in volume 5 to 6 hours.
Step 2
Stir 1 cup all-purpose flour 1 cup whole wheat flour 1/2 water sunflower seeds polenta flax seeds salt and honey into sponge with a wooden spoon until a very sticky dough ball forms about 3 minutes. Scrape down the the sides of the bowl cover bowl with plastic wrap and let dough rise until doubled in volume 10 hours to overnight.
Step 3
Line a baking sheet with parchment paper. Dust parchment paper with 1/2 teaspoon all-purpose flour and cornmeal.
Step 4
Scrape dough out of bowl onto a lightly floured work surface press down to remove air and form into a smooth oval loaf. Place dough on the prepared baking sheet. Dust top of loaf lightly with flour cover with plastic wrap and let rise until doubled in size about 1 1/2 hours.
Step 5
Preheat oven to 450 degrees F (230 degrees C). Place a baking dish filled with water on the bottom rack of the oven.
Step 6
Remove plastic wrap from risen dough and mist the top of the dough with water.
Step 7
Bake loaf in the preheated oven misting the top of the loaf with water every 8 to 10 minutes until loaf is golden and sounds hollow when tapped 30 to 35 minutes total. Transfer bread to a cooling rack and let cool completely before slicing.