With Mote installed in Chrome you can simply click the Mote icon while editing your Google Slides to record and insert narration into your slides with just one click. Watch this demo to see how quick and easy it is to add audio to Google Slides through the use of Mote.
Thanks to Ellen, a loyal reader of my blog, over the weekend I learned that Mote is making some changes to their pricing model in 2022. The free version of Mote will be limited to twenty recordings per month beginning in January. That should still be plenty of recording time for students to use to add narration to Google Slides. Here's more information about the change to Mote's free and paid plans.
On a related note, here are five things you should know about using audio in Google Slides.