In most situations, an undercooked loaf of bread can be fixed by returning it to the oven for a few more minutes. This is true for loaves where the outside of your bread may look fully set, but the inside of the bread is still gummy. Place the loaf back in a preheated oven at 350° F for 10-20 minutes. You can tent the bread loosely with foil to prevent it from browning further, if that’s a concern.