It has always been very easy to insert videos into your Slide presentations because you simply used YouTube videos. However, if you wanted to use a video of your own you had to first upload the video to YouTube and then pull it from YouTube. Now you can insert your own videos directly from your Google Drive.
Simply go to Insert/Video, and you will now see a third option "Google Drive".
After you have inserted the video from your Drive, you can choose when to start and stop the video and if you want the video to autoplay when you are showing the slide. You can also choose to mute or play the audio.
So get your phones out and start making those videos and sending them to your Google Drive. It has never been easier to put those videos in your Slide presentations.