Anyway, if you're a long term follower of the blog, you might remember that I did something similar to this several years ago (i.e. before I started the youtube channel) - but I've refined the process slightly since then ...as you'll (hopefully) see in the video:
I've also uploaded a new pdf file for this specific purpose (which can be downloaded HERE) ...and, as usual, it's a pay-what-you-want product - so pick it up for free OR pay as much/little as you like!
But yeah ...I'm pretty happy with how these have turned out - and already have a few ideas for a 'collapsing dungeon' scenario. So here's hoping you'll be able to put them to use in your own games too :)