In a large bowl, whisk together the bubbly, active sourdough starter and the filtered water. Add the all-purpose flour and bread flour. Use a wooden spoon or spatula to combine. The mixture will be wet and sticky. Sprinkle it with salt, and gently pinch it with your fingers. Cover with plastic wrap and let rest for 1 hour.

After 1 hour, leave the dough in the bowl, and complete 4 sets of "stretch and folds." These will be completed in 30 minute intervals.

Stretch and Folds: Wet your hands with water, and grab a piece of dough near the top of the bowl. Pull it straight up to stretch making sure not to tear the dough. Fold it over to the center of the dough and press down lightly. Repeat this on each side of the bowl and the bottom. You'll do this 4 times (think of the bowl in fourths or quarters). After completing a stretch and fold in each quarter of the bowl, that is a "set." Complete 3 more sets of stretch and folds at 30 minute intervals over the next hour and a half, and cover with plastic wrap between each.

After completing all 4 sets of stretch and folds, cover the bowl with plastic wrap, and refrigerate for 8 hours or up to overnight. When you're ready to work with the dough again, remove it from the refrigerator, and allow it to come to room temperature, about 1 to 2 hours. While the dough warms, oil a 9 x 5-inch loaf pan with your choice of cooking oil. Set aside.

When the dough has warmed a bit, transfer it to a lightly floured work surface. Lightly flour a roll pin, and roll the dough into a flat, rectangle shape. Press as many of the air bubbles out of the dough as you can. Any leftover air bubbles will make holes in the baked sandwich loaf.

After you finish shaping a rectangle, wet your hands and a bench scraper. Starting with a long side of the rectangle, gently fold ⅓ of the dough over to the center. Repeat on the other side. There should be a seam down the middle of the down where the two sides meet. Gently pinch the seams shut.

When the bread is ready to bake, preheat the oven to 400°F. Bake the bread for 40 to 45 minutes or until the top is golden brown. If the top begins to brown too quickly, fold a piece of aluminum foil and loosely drape it over the top. I usually do this about 20-25 minutes into the baking process.

Remove the bread from the oven, and let it cool in the pan for 5 to 10 minutes before transferring it to a cooling rack. Allow the bread to cool completely before slicing.

Store any leftovers in a plastic zip bag. The leftovers stay fresh for about 2 days.