Well, this one is both kitbashing and scratch build. Most of the scratch build is sort of fill in the gap thing with this one.
I scratch built the hands since I can't find one with good proportion. Then the legs because the thigh, knee and bottom leg is joint together with no articulation whatsoever so I scratch build that. The toes also joint together so I scratch build the articulation for each one.
Scratch build is very challenging but fun when things come together.
In the end I think I prefer kitbashing and modding compared to this. But I feel like I can make anything after having done quite a bit of scratch builds.
I've checked this Blackadder you mention and his builds are crazy I wonder how much time did he spent on making them. Also the details are amazing!
How about yourself? Do you build model kits?