It can be a very challenging method, but one that also allows for a great deal of flexibility in post-production. Each of the 'frames' were hand written on a white board, then composited in After Effects 3d space with camera moves. It involves a great deal of pre-production work to ensure that everything is going to fit where it needs to, and a lot of oversight during the shoot to make sure everything is both included and (we discovered) spelled properly :)
Click below for the spot!