Issues while following the documentation for thin jails using UFS in Chapter 17

Hi,

I am having a rough time while trying to learn how to implement thin jails in a FreeBSD system operating in UFS. This corresponds to Chapter 17 of the handbook.
I followed the handbook carefully three times without success. I have been also trying to get some support from both the FreeBSD forums and from libera FreeBSD IRC channels without success. I have also read the man page for jail.
Essentially trying to follow the steps for thin jails from the handbook leads me to:- Not being able to understand the role of different directories, role of template -if any-, mount points and role of NullFS in Thin jails.- Not being able to reach a working system by carefully following the steps given in the handbook.
The steps and errors are documented here:
Thread 'Issue while following the handbook to create a Thin Jail using NullFS'
https://forums.freebsd.org/threads/issue-while-following-the-handbook-to-create-a-thin-jail-using-nullfs.91015/
If I can further help or test or even amend the documentation I would be glad to contribute, but at this point the problem is that the information is not enough to even understand the topic first.
Thanks,