There are plenty of ways to

There are plenty of ways to do this; flash drive is one of them, like you mentioned. This article is perfect for you, go ahead and check it out: https://valoso.com/blog/deliver-client-video-files/

The article outlines these delivery methods for HD videos:
DVD
Cloud storage services
File sharing apps and websites
BitTorrent (or any other torrent)
FTP servers

Just make sure you have the file in HD stored on your computer. Depending on what your business is looking for with speed, security, and storage, every method of delivery is different.

Hope this helps!