I have always been a huge fan of EdPuzzle. This Chrome Web Store Extension will allow you to use video from many popular sites and modify it for your requirements. It is the ideal tool for flipping your lesson.
An example of how to use EdPuzzle, you found a Crash Course video that you want to use, but only parts of it apply to your lesson. After installing the extension you will see a new EdPuzzle button on the video’s YouTube page. After clicking on the button and signing into EdPuzzle you will be presented with 4 tools. You will be able to trim the length of the video, you can replace the entire audio track with your narration, you can pause the video and insert an audio note (reminds me of when I would pause the VHS video and provide commentary to my class), or you can insert a formative quiz. After preparing the video, you can share it in Google classroom or any other LMS that you are using.
If you would like more information about flipping your lesson, check out this resource from Anita Brooks Kirkland and myself.