How does one make one of these. Is it complicated?
There are lots of difference methods, and even apps, to do this.
But they will all need a set of still images to feed on.
IP cameras often have a 'capture' facility where they can be configured to dump an image on a specified repeating schedule into an FTP destination.
As a Linux user, I tend to use the versatile tool ffmpeg to convert the resulting set of still images into a video file.
Example :
ffmpeg -v verbose -framerate 25 -pattern_type glob -i '192.168.1.66_01_202*.jpg' -r 25 -c:v libx265 video1.mp4