I just recalled that rarest of things, the really good teacher. Not merely competent, but so good that you wonder how they did it.
I had a teacher for an early algebra class in high school who was that good. I still don't know how he did it. Other teachers could take a 50 minute or so class period and use it all, and despite talking a lot, not really say much. This guy was different.
A typical class would start with him talking about... well, pretty much anything. Maybe something he did or saw the night before. Maybe a bit of local news. Maybe something bigger. But not related to the class - he didn't use it a segue into the lessons. Once finished with that, he'd teach the lesson of the day, or go over whatever was to be studied and worked on at the time. Now, you'd expect that this would take up the rest of the class time, and sometimes it did. But often it did not. So the last part of the class was used to start the assignment - and allow questions to occur while we were there to ask and he was there to answer.
I've forgotten, at least at the moment, his name (Addendum: I think it was Schneider). But I do remember the class and how it was relaxed but not slack. And I wish there more teachers like him.