I had an hour to kill at a hardware store a few days ago, so I walked up and down the aisles trying to think of how to put various tools and objects to use carving ice. I picked up a Strong-Tie MP36 Mending Plate and thought it might make a decent, one-handed nailboard. (As my friend, Dave, would say, "This nailboard was mislabeled as a mending plate.")
I tried it today, and it works great! I guess I shouldn't have spent all that time making my wooden nailboard. Attaching a whole bunch of these mending plates to a board would be a very quick way to make a large nailboard.