Add sourdough starter, flour, salt and 1 cup water to mixing bowl. Using a dough hook begin mixing on low speed.
Continue mixing for 3-5 minutes, adding water or flour if needed. Keep in mind the dough will continue to moisten as it mixes. (You’re looking for a slightly sticky dough that wants to stick to your hand, but releases when you quickly pull away.)
While dough is mixing, grease your loaf pans.
Once dough is smooth and elastic, scoop it out and begin to fold it in on itself, shaping it into a long loaf in your hands (kind of like a hotdog bun, then sealing off the crease). If using two smaller loaf pans, be sure to divide dough in half.
Place dough into greased pans. Slice lengthwise, about 1/2 inch deep, down the top with a sharp knife (to promote a nice rise).
Loosely cover loaf pans with plastic wrap.
Let bread rise until doubled (may take 6-12 hours depending on the temperature of your kitchen).
Once dough has risen, preheat oven to 375℉. (You may melt a tablespoon of butter on the stove and brush the tops before baking if you’d like, this makes for a very pretty golden brown top, but is not a necessary step.)
Bake for 45-50 minutes, until top is golden brown and bread sounds hollow when thumped with your finger.
Immediately remove from pan and allow to cool completely on wire rack before slicing (if you have enough self-control!).
Once bread has cooled completely, store in a bread box or wrap in aluminum foil.