My loaves often cracked at the base during baking even though I sliced the top to allow for expansion. I thought this must be caused by the crust forming too quickly and air finding the easiest escape route out the bottom. The bread still tasted great but it didn't rise properly and it didn't look professional. I experimented with spraying water or adding a few ice cubes to a tray in the bottom of the oven but to no avail. After a lot of experimentation I discovered that a tray filled with water in the bottom of the oven did the trick. I guess the high humidity in the oven allowed the bread to fully rise before the crust formed. Now I consistently get nice looking loaves like this one. Just thought I'd share this in case anyone else out there was having a similar problem.