In a large bowl, add sourdough starter, water, sugar, cinnamon, and flour. Mix to form a shaggy dough. Cover and let sit 20-30 minutes.
Sprinkle salt on the dough and pinch to incorporate.
With a wet hand, take one quarter of the dough, stretch, and fold over the dough. Turn 90° and repeat for a total of 4 stretches and folds. Flip the dough over, cover, and let sit 30 min.
Repeat step 3 for a total of 5 rounds of stretch and folds over approximately 2.5 hours.
On a lightly floured surface, dump out dough and pull in the edges and flip to form a round. Continue to tuck and turn to form nice tension of the dough.
Flour the top and place upside down in a well floured bowl or banneton. Cover and let sit 1-2 hrs. Then refrigerate overnight.
The next day, preheat your oven to 450℉ with the dutch oven inside. Place a baking sheet on the rack below. This helps to prevent the bottom of your loaf from getting too dark.
When the oven is hot, flip the dough out onto a piece of parchment paper. Score the top with a sharp knife or scoring blade. Then, gently place into the dutch oven.
Place cover and bake for 30 min. Remove cover and bake an additional 15 minutes.
Place on a cooling rack and let cool for 45 minutes before slicing.