I record from the microphone, re-recording until I am satisfied, and using the Delete before and Delete after options to trim off unnecessary silences. Then I select Exit and click Yes when asked to update. The document now has a microphone icon at that point and will have grown by about 10K for every second of sound. That may seem rather a heavy use of memory, but I find a minute or so of single words and short phrases, recorded without pauses, is a lot of data. Most of my documents are well under a megabyte.
Active documents are essentially dictation exercises.
You could make them in the same way and make multiple copies, one for each person in the class, but that might use up unacceptable amounts of disk space. Could I just have your attention please. There are one or two announcements before we break up for lunch. First of all, could you all make sure you have registered and collected your room keys. And if you have come by car, could you make sure you leave it in one of the bays numbered 14 to 60.