Replace "jaileduser" with whatever you want the username to be.
Step 1 (as root) - Setup chroot environment and user. Replace fish
in the last command with whatever shell you want.
sudo su -
mkdir --parents /home/jaileduser/home
useradd --create-home --gid users --home /home/jaileduser/home/jaileduser jaileduser
usermod --home /home/jaileduser jaileduser
mkdir --parents /{etc/jail/jaileduser,var/jail/jaileduser/{cache/{key,pkg},lib}}
chown jaileduser:users /var/jail/jaileduser/cache/key