/Applications/Install/ does not appear to be a valid OS installer application

This is an answer instead of a question, but I wanted to post it somewhere to help others.

I followed the Macworld post "How to create a bootable USB macOS installer" and got that error. After hours of searching and trying suggested fixes, I finally noticed that the instructions were wrong. The "--applicationpath /Applications/Install/ macOS/ Sierra.app" part obviously uses '/' instead of '\' to protect the spaces. Duh.