Gather all ingredients and ensure your bread machine is clean and assembled.

Pour 1 cup of warm water (about 110°F) into the bread pan, then add 1/2 cup active sourdough starter.

In a bowl, whisk together 3 cups bread flour, 1 teaspoon salt, 1 tablespoon sugar, and 2 teaspoons bread machine yeast until evenly combined.

Add the dry ingredient mixture on top of the wet ingredients in the bread pan without stirring.

Select the basic bread setting on your machine and start the cycle, which will run for approximately 3 hours.

After 5 to 10 minutes of mixing, check the dough; it should form a smooth, elastic ball. If too dry, add a teaspoon of water; if too wet, add a teaspoon of flour.

Allow the bread machine to complete the mixing, rising, and baking cycle (about 3 hours in total).

When the cycle finishes, carefully remove the loaf and let it cool on a wire rack for at least 30 minutes before slicing.