I was really ambitious at the start but it made my brain hurt I ended up just copy/pasting the first one and using it as a base >.> (cheating?) So, about ten minutes.
My wife designs Halloween costumes for a living, and that's the way she does it—some time ago, she drew up several "models", and she just copies and pastes them into her new files when she draws up a new costume
So it's not cheating: it's the same kind of trick the pros use!
Me, I'm not even skilled enough to achieve what Artemesia did