1. Combine the Wet Ingredients: In a large mixing bowl, gently whisk together the active sourdough starter, warm water, sugar, and salt until the sugar and salt are mostly dissolved. The mixture should look slightly milky and have a few bubbles from the active starter.

2. Add the Flour and Mix: Gradually add the 5 cups of all-purpose flour to the wet ingredients. Use a sturdy spoon or your hands to mix until a shaggy, sticky dough forms and no dry flour remains. It won’t be smooth yet, and that’s perfectly normal.

3. Knead the Dough: Turn the dough out onto a lightly floured surface. Knead for about 8-10 minutes until the dough becomes smoother, more elastic, and less sticky. If it’s too sticky, lightly flour your hands and the surface, but avoid adding too much extra flour. The dough should pass the “windowpane test” – you should be able to stretch a small piece thin enough to see light through it without tearing.

4. First Rise (Bulk Fermentation): Lightly grease a clean large bowl with olive oil. Place the kneaded dough into the bowl, turning it once to coat all sides with oil. Cover the bowl tightly with plastic wrap or a damp kitchen towel. Let it rise in a warm spot for 4-6 hours, or until it has visibly doubled in size. Alternatively, for a longer, slower rise and more flavor development, you can place it in the refrigerator for 8-12 hours (or overnight).

5. Shape the Loaf and Second Rise: Gently punch down the risen dough to release the air. Turn it out onto a lightly floured surface. Shape the dough into a tight rectangle or oval that will fit into your loaf pan. To do this, gently flatten the dough, then fold the top third down to the center, and the bottom third up over that. Pinch the seam closed, then roll the dough into a log, tucking the ends under. Place the shaped dough seam-side down into a lightly greased 9×5-inch loaf pan. Cover the pan loosely with plastic wrap or a damp towel and let it rise again in a warm spot for 1-2 hours, or until it has nearly doubled in size and looks puffy.

6. Bake the Bread: Preheat your oven to 375 F (190 C) during the last 30 minutes of the second rise. Once preheated, place the loaf pan in the center of the oven. Bake for 35-40 minutes, or until the crust is golden brown and the internal temperature reaches 200-210 F (93-99 C) when checked with an instant-read thermometer. If the top is browning too quickly, you can loosely tent it with aluminum foil for the last 10-15 minutes of baking.

7. Cool Completely: Immediately remove the bread from the loaf pan and place it on a wire rack to cool completely before slicing. This is crucial for the internal texture; slicing too early can result in a gummy crumb. Allow at least 1 hour, but ideally 2-3 hours, for the bread to cool.