In a large mixing bowl, mix together the Biga and water with your hand or a whisk till it dissolves. Add the flours, salt and the water and mix together with a wooden spoon until the flour is just incorporated. Cover loosely and let it rest for 20 minutes.
Every 30 minutes, stretch-and-fold the dough over itself from all four "sides" until you have done this 6 times (over 3 hours). At this point, the dough is ready to shape.
Line a banneton or bowl with a tea towel, and sprinkle it generously with the rice flour. Turn the dough out onto a lightly floured work surface, and shape it into a tight ball. Place the dough, seam side up, into the prepared banneton/bowl, and cover with oiled cling wrap. Let rise until doubled. Depending on ambient temperature, this takes between 1 1/4 hours to 3 hours.
Once the dough has doubled in size, remove the Dutch oven from the oven and remove the lid. Place a piece of parchment paper lined plate over the dough, and flip the dough over so that the bowl is upside down. Remove the bowl and the towel. Lift the dough, parchment and all, and place the dough into the Dutch oven. You can use a pre-heated Dutch Oven but this time I worked with a cold Dutch Oven.
Slash the dough in a triangle pattern, cover with the lid, and place the pan in the oven. Bake at 230C (450F) for 35 minutes with the lid on. Remove the lid , and bake for another 10 to 15 minutes, until the loaf is done and the crust is dark brown.
Cool the loaf on a wire rack for at least an hour.