Grace's Sourdough Bread Guide:

What You'll Need:

Sourdough Starter that doubles in size within 12 hours after feeding at room temperature. (The link to Sourdough Starter Guides that Grace used can be found below).
Large Mixing Bowl
Scale
Proofing Basket with Liner, or a Dish Towel
Bowl Scraper
Dutch Oven or Bread Cloche (Oven Safe up to 500° F)

Add flour and water. You can use any combination of flour that adds up to 500 grams, altogether. Grace recommends that the majority be bread flour. For this loaf, we used 450 grams white bread flour, 25 grams rye, 25 grams spelt. Add between 70 - 80% of the flour's weight in tap water. Grace did 75% of 500 grams (which is 375 grams of water). Mix until shaggy - you want all of the flour to be wet. Let rest for one hour. This part of the process is called "autolyse".
Add 20% of the flour's weight in ripe (doubled and bubbly) sourdough starter. In Grace's recipe, this calculated to 100 grams. Mix gently.
Add 2% of the flour's weight in salt. In Grace's recipe, this calculated out to 10 grams. Mix your dough with the "Stretch and Fold" motion for about 10 minutes. Let rest for one hour. This part of the process is called "Bulk Rise" or "Bulk Fermentation".

After one hour, wet your hands and gently stretch and fold the dough 4 times. Let rest for another hour. Repeat this process of resting and then folding 3 to 7 times, or until the rested dough has doubled in size and large bubbles have formed on the surface.

Lightly flour a clean surface and pour the dough out onto it slowly, taking care to not pop the bubbles that have formed. Use your bowl scraper as needed to help transfer the dough if it is sticking to the bowl. Lightly flour your hands and fold the dough, much like an envelope, then cover it with a towl and let it rest on that surface for 30 minutes.

Generously flour your proofing basket.
Shape your dough to fit the shape of your proofing basket. Grace used a round basket, so they shaped the dough into the shape of a ball.
Transfer the dough into the basket (seam side down) and generously flour the sides of the dough so that it doesn't stick to your liner or dish towel. Let it rest at room temperature for 40 minutes to 1 hour, or until you can poke it with a floured finger and it springs back slowly.
Refrigerate for an hour or up to 3 days - until you're ready to bake it. Cold dough is easier to score, which is why it's important to refrigerate it, even if you plan on baking your loaf right after the final proof.

Preheat the oven to 500° F with the dutch oven or bread cloche inside the oven. Grace preheated her dutch oven without the lid just to make transferring the dough easier later, but you can preheat the whole thing if you prefer. ** If using a cloche, preheat the whole cloche. Let the oven heat up for around an hour to make sure the heat is evenly distributed.**
Take the dough out of the fridge and coat the top with flour. Turn the basket out onto a piece of parchment and carefully peel off the liner. You can coat this side of dough with flour as well, but it is purely an aesthetic choice. Quickly and deeply slash the top of the loaf with your lame.
Take the dutch oven or cloche out of the oven and use the parchment to help lift the dough into the dutch oven. Cover with the lid and bake at 500° F for 20 minutes.
Reduce heat to 450° F and remove the lid from the dutch oven, continue to bake for 30-40 minutes, or until the top of the bread is deep golden and brown.
Turn the bread out onto a cooling rack and let it rest for at least an hour. If you cut into it too early, the texture can turn out gummy. Enjoy!