Hah, OK. The one I used in the first video was super crude. The one I used in the last video was something I 3D printed, but it didn't work as-printed, so I modified it with some popsicle sticks. You should be able to get the general idea, it's a pretty simple concept.
I've done things like that before, but making sure the framing is correct was always the challenge. With an iPhone and Apple Watch, that's super easy since you can remotely view and control the phone camera from the watch!
Chris