I haven't attempted to tie it myself yet but SF describes the fly well in the video.
I believe the hollow tie method was created by Bob Popovics. He ties the material in backwards and then uses a tube (empty pen case) to push it back and wraps bucktail in front (NOT ON TOP) to flair the material.
It looks to be a good big bait profile such as bunker or herring without all the bulk that makes other big flies difficult to cast.