Some of this may be slightly different in FFT, but in general...
You can hide conferences altogether in course settings > navigation. Just drag conferences (and any other tab you will not use in this course) below the divide, and then click save at the very bottom of the page. You can change this as often as necessary. (For example, at the beginning and end of a school day, if you only want this to be possible while you are monitoring.)
If you want to run conferences without letting students run their own, an admin can restrict access for all students at your institution. Then you would keep conferences in the navigation menu, but students would only have the option to join a conference started by you.
If your institution lets students start a conference, and as an instructor, you join a conference started by a student, you will automatically have moderator permissions: https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-join-a-conference/ta-p/961 You should be able to start the recording yourself at that time.
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