Board Thread:General Discussion/@comment-25266931-20151115205337/@comment-4010415-20151125225719

For the most part, it is made beforehand. It's just that it's not complete yet when they start airing the episodes.

They get the principle animation done before they start releasing the episodes - the bare basic stuff of the characters' movements and such. Then, they start polishing it up with effects and whatnot. I have no clue if facial expressions and lip synching are part of the principle animation or the finishing touches. They also have to go through and try to make sure there aren't any errors in the animation, though of course, as we've seen, they do miss some things, such as improper layering and missing or misplaced models. They also have to put the audio in there - the voices, the sound effects, the music and ambience.

Animation goes in stages. If they took the time to complete the entire volume 100% before airing the episodes, we'd have to wait a lot longer for the volume to start coming out.