Hi @cyberdave, thanks for sharing, this is exactly what I was looking for. I have some feedback to give, though.
This is a Webflow article’s printscreen:
It’s necessary to fix the script box, because the text is passing the purple area. Also, to fix Add code before ” tag” panel to Add code before < /body> tag. Despite being a simple adjustment, it would be very useful for non-programmers – like me 
And the most important: the article should guide to replace the “my-video” text for the Youtube Video ID in the Embed Widget (ID, Name and Src) and Script. Telling this because it wasn’t explicit and I struggled to find why the whole thing wasn’t working. Again, simple but not for non-programmers.
To finish, I’d suggest a tutorial’s update for the iFrame Player API, as “YouTube JavaScript Player API have all been deprecated as of January 27, 2015”.
Hope you find the feedback useful.