FTP server on IIS

I recently had cause to set up an FTP server for internal use on a Windows server, and I bumped into an issue that took me a little while to figure out, since I had never done it before:
I wanted to give a domain user account an isolated directory, and started out by creating the user directory inside the inetpub\ftproot folder. However when I tried to log on with a client, it would I’ve me an error message “530 User cannot log in, home directory inaccessible”.

Turns out the answer was simply to create a subdirectory to the ftproot with the name of the domain, and then move the user directory inside that one.