Successfully made my first sourdough Monday!

Used sprouted grain whole wheat, everything went well. Only critique my wife had was "the bottom is a bit hard to chew through." She's right, when eating a slice you really have to tear and gnaw at the bottom part (the part that sits in contact with the cast iron). Anyone have any pro tips so that the loaf gets baked enough but the bottom isn't such hard work? Did I maybe bake it too long?