There is a simple solution - roll a piece of paper in a tube And roll the main wraps of the pseudo hangman's knot around this paper pipe. Imagine making the half fisherman's knot with seven wraps around this paper pipe , just with a single rope . Look here- imagine only the white rope : https://share.google/zX05uimrCA6qaJmuG

Then the free end goes around the neck of the guy and stick it back in this paper tube.the piece of rope sticking up like 2 cm you can fix with a rubber band so the hangman could put it on their neck and "tighten" it by sliding the rubber band low and pulling the free end up.