In a medium bowl, stir together 45 grams of starter and 315 grams of water.
Add in 450 grams of bread flour and mix in 9 grams of salt.
Mix that with a spoon, and when it’s tough to mix, you can squeeze the dough together with your hand. This helps to get the little bits of flour incorporated into the water.
Cover with plastic and let it sit on your counter for about 1 hour.
After the hours, form this into a ball. Pull up on the edges, and then place it in the middle of the dough. Do this about 10 times around the dough to form a ball. Cover again and let sit for 30 minutes. After 30 minutes, you begin your first of 3 sets of “stretch and folds”. Instead of pulling up about 10 times like you did before, this time you’ll do 4. Take about 1/4th of the dough, stretch it up as high as it can go without ripping, and place it on the opposite side. You can use two hands to stretch it up, or 1 hand to stretch, and 1 hand to hold the bowl. After you've gone around 4 times, cover, and let the dough rest for 30 min. Repeat this stretch and fold process 2 more times, with 30 min between each set.
After your third and final set of stretch and folds, cover with plastic, leave on the counter, for up to 12 hours. This is the bulk ferment. It can ferment in summer faster than in the winter. When it's doubled, it's ready to be shaped.
When the dough has doubled, roughly 8-12 hours later, dump the dough out onto a very lightly floured counter (gluten free flour). It will look wet and loose. We are going to form it.Lift the outside edges up and bring them together in the middle of the dough to create the basic shape of round bread dough. Now that it is in something of a ball shape, roll the dough over so the pinched together side is against the counter. Lightly cup the dough with your hands, twist and pull it towards you. You will start to see a skin form along the top, with tiny air pockets just under the surface. Complete about 5 or 6 of these pull and turning motions to get the skin of the dough into a tight, smooth, ball. Flour a tea towel or banneton liner with gluten free flour.Place the dough into the floured bowl/banneton with the “skin” side down. The sticky side should be facing up. Then fold the towel lightly over the dough. Place this in a plastic bag and tie. Keep this in the refrigerator for 8-36 hours. This is a cold ferment. When it's time to bake, 8-36 hours later, preheat your oven to 500 degrees with the dutch oven inside. Once your oven hits 500 degrees, take your bread out of the refrigerator. Gently dump out the dough onto parchment paper so the smooth floured side is face up. Cut an expansion score in the bread about 1/2" deep with a lame or sharp knife.
Using the parchment paper to carry the dough, place it in the dutch oven, lower the heat to 450, and bake for 30 minutes with the lid on.After 30 minutes, remove the lid and bake for 10 - 15 minutes to achieve the level of browning you desire. Allow the bread to cool, and then enjoy!