Add all of the ingredients to a large mixing bowl except for the salt and mix with a spoon or spatula. Let rest for 20 minutes.
3 cups (375 grams) bread flour, 1 cup (240 milliliters)warm water, 1 teaspoon instant yeast, 1 cup (113 grams) sourdough discard
Add the salt and knead until the dough is smooth and passes the windowpane test. The dough should be slightly tacky. If the dough is full on sticky, add a tablespoon of flour at a time, or add a teaspoon of water if it is dry. If adding seeds or nuts, add them at the end of kneading and knead by hand to incorporate.
1½ teaspoon (5 grams) kosher salt
Shape the dough into a ball, cover with plastic wrap, and put the bowl in a warm location until it has doubled in size, about 1½ hours. The microwave or a 80°F oven works well here.
Shape into a sandwich loaf and let rise in a greased 9 by 5 inch bread loaf pan until it is about an inch over the side of the loaf pan, about 1½ hours.
butter or cooking spray
Preheat the oven to 375°F at least 30 minutes before baking.
Bake your sourdough discard sandwich loaf for 30 minutes until it is golden brown, the internal temperature is 190℉, and it sounds hollow when thumped on the loaf bottom.
Remove the sandwich bread from the loaf pan immediately, and let cool on a baking rack for at least one hour before cutting.