Holy oven spring, Batman!!
So, after yesterday's success I tried again with the 123 sourdough recipe but this time I used half freshly ground whole wheat (that I soaked for about 12 hours) and half bread flour. I basically did everything the same as yesterday, but this time I proofed it in a flour covered kitchen towel in my salad spinner (I know, I'm super authentic). The final shape before hitting the oven was round, but not like this volcano.
Did it it not proof long enough? Did I score too close to the middle of the loaf? Or is this just what happens when you proof in a basket type shape? I haven't cut it yet because it's still hot.