This page discusses known working practices for creating videos from PowerPoint slides with an audio commentary. Some of these techniques will work for instructional videos, etc., but that will not be discussed here.
Stanford provides access to Zoom for all faculty, staff, and students. This is the easiest method to use if the presentation is to be shared with others both inside and outside of Stanford. Please note that PowerPoint presentations containing videos will likely not record correctly, provide any supplemental videos as separate files.
Make sure have a microphone connected (unless on a laptop with built-in microphone), a camera is not required. To log into your personal Zoom account, open this link, then click on Log In which will take you to the normal Stanford login page. Once authenticated, you will go to your Zoom profile page. Click on Meetings in the left menu, Personal Meeting Room to get to your meeting page, then the Start Meeting button. This may cause your browser to pop-up a dialog asking if it's OK to open zoom.us, confirm if necessary. If not already present, the zoom.us application will download and install, your OS may ask if it's OK to run this program. On startup, the application will first pop-up a dialog giving you the option to Join With Computer Audio or Test speaker and microphone. Assuming your hardware has been properly set up, click on Join With Computer Audio to initiate a meeting. Do not click Start Video unless absolutely necessary, as video will greatly increase the size of the recording. Start PowerPoint and open the desired presentation file, but do not start the slide show yet. When you are ready to record your presentation, go back to the Zoom app and click on the Share icon, then double click on the thumbnail image for the presentation application (or select it and click the Share button). The PowerPoint window should now be highlighted, go back to it and enter slide show mode. Make sure the actual slide show screen is highlighted, it may not be if you have more than one display (if this is a problem, select the proper desktop thumbnail for sharing, not the PowerPoint app). If the Zoom icon menu is not visible (which will happen if you only have single display) move your cursor to the top edge of the screen to make it appear. Once visible, click on the Record icon (if present) or More. Click on Record to the Cloud (you can record directly to your computer, but that adds complexity, see the help page linked below for more information). Run through your presentation, then move the cursor to the top of the screen, click on More, the click on Stop Recording. Now click on End Meeting, then click on End Meeting for All in the dialog box. An email should be arrive shortly indicating the recording is available, it contains two links, one to the recording details (which is only accessible to you), the other link is used to share the recording with viewers, anyone provided with that link will see the recording.
You can see all of your recordings by visiting the Recordings page in your Zoom personal profile. There you can see the details of each, obtain the sharing link, download, and delete the individual recordings and files. If you download a recording, it may consist of several files, see the link below for more details. One limitation is that if you want to record video along with a presentation, or record more than one presentation in the same video, these will be broken out into separate files. The only way to see the the recording as a whole is to use the cloud links. Be aware that Zoom limits each user to 1 Gb of storage, delete or download recordings that are no longer needed to free up space for new recordings.
Alternatives to Zoom
If your requirements can't be met using Zoom, there are alternatives available. MacOS has built-in screen recording capability in the latest releases (10.14 Mojave or later) or use the QuickTime Player for earlier versions, read this article for details.