Add all ingredients in the order given: 1 cup water, ⅓ cup sourdough starter, 1½ teaspoon table or sea salt, 1½ teaspoon granulated sugar, 3 cups bread flour, and 1½ teaspoons instant or bread machine yeast.
Choose the DOUGH cycle and hit START.
15 minutes into the DOUGH cycle, lift the lid and check the dough. It should be tacky enough to stick to the sides of the pan, then pull away cleanly. If too wet, add flour 1 tablespoon at a time. If too dry, add water 1 tablespoon at a time. Give the machine 2-3 minutes to knead in the flour or water before adding more.
When the DOUGH cycle is complete, check the dough. It should be double the original size. If it has not risen enough, leave it in the machine until it does.
Remove the dough onto a floured or wet surface I keep a spray bottle handy. Press the dough into a rough rectangle. The short side should be slightly wider than the length of your bread pan.
To make a loaf, roll the dough into a cylinder starting from the short side. Seal the seams and turn the ends under and pinch shut.
Place dough with the seam down into a greased 9 x 5-inch loaf pan. The dough should not fill the pan more than half full. If the pan is too full, use a larger pan or pull out some of the dough and make rolls with the extra dough.
Set the prepared loaf in a warm place, cover, and allow to rise again until approximately one inch above the top of the pan.
Meanwhile, Preheat your oven to 450˚F (230˚C).
When your loaf is ready to bake, sprinkle the top with flour. Make slashes diagonally or one slash lengthwise down the middle.
For a crispier crust :(optional), place a pan containing 2 cups of boiling water onto the bottom rack of your oven while the bread bakes. Spritz loaf lightly with water a couple of times in the first five minutes to add steam.
Place bread in the oven and turn the oven temperature back to 425˚ for 25-30 minutes. The loaf is done when the internal temperature reaches 200-210˚F.
After ten minutes, remove baked bread from the pan onto a cooling rack so the bottom won't steam and get soft.
Allow your bread to cool at least one full hour before cutting into it. Failure to wait will cause the bread to be gummy.
Notes
For a more pronounced Sourdough Flavor:
The day before you want to serve the bread: Combine all of the water, sourdough starter, and half of the bread flour in the bread machine pan. Start the machine and let it mix just until all the flour is moistened. Turn the machine off. Let this mixture sit until you are ready to make bread the next day.
Making the bread: Add the salt, sugar, remaining flour, and yeast. Mix on the DOUGH cycle. Proceed to Step 4 and finish making the bread as directed.