In a small bowl, prepare your cinnamon swirl filling by whisking together the brown sugar, cinnamon, and flour until well combined. Set aside.
1/2 (67g) cup brown sugar, packed, 2 (16g) Tablespoons all-purpose flour, 1 1/2 (10g) Tablespoon ground cinnamon
Lightly flour your work surface to prevent sticking, and grease your loaf pan with a light coat of oil or nonstick spray.
Gently turn your dough out onto the floured surface. Using a rolling pin, roll the dough into a large rectangle approximately 10x20 inches (bottom and top being 10 inches). The width should match the length of your loaf pan; the longer the rectangle, the more distinct the swirl will be.
Evenly sprinkle the cinnamon sugar mixture over the surface of the dough, leaving a ½-inch border along the edges to help seal the bread.
Starting at the bottom (the edge closest to you), gently roll the dough up into a tight log using your hands or a dough scraper to help lift and tuck as you go. Once rolled, pinch the seam closed along the top and seal the ends by pinching and tucking them under slightly.
Carefully transfer the rolled dough into the greased loaf pan, seam side down. Cover loaf pan with plastic.
NOTE FOR OVERNIGHT REFRIGERATION AFTER SHAPING: At this point you have the option to cover the loaf in the pan with plastic and refrigerate overnight for longer fermentation, or proceed with proofing and baking.
If you choose to refrigerate overnight, do not proof after shaping. Bread will proof in refrigerator in pan, but will need additional proofing time at room temperature the next day. Allow the bread to come to room temperature the next morning and proof 1-2 hours or until dough is risen over the edge of the pan and proceed with baking instructions as listed below.
IF SKIPPING OVERNIGHT FERMENTATION: Let the bread proof at room temperature for about 1 hour, or until the dough is just peeking over the edge of the pan. See the picture above for how the bread should look before baking.
Note: If you over proof the bread while it's in the pan, you will end up with a distorted swirl.