I suppose he at least had drawings as a model or even a kit. He will hardly have designed the aircraft himself.
In addition, each aircraft must be inspected and approved by the aviation authority.
With a little skill, time and money this should be feasible for everyone. Provided you have a pilot's license.
Yes anyone with a modicum of skill and lots of patience can do it. My Jodel was built from plans in 1964 by a licensed aircraft engineer but many amateurs built them as well. The Kitox was built from a kit by me and a mate. I restored the Auster (under supervision) and I am really an amateur i.e. no technical training. From the video I think that Czech builder is quite exceptional.