Great question — answering as the UphillTech team:
This looks like your XFCE desktop doesn't get started by Slim. Have you created the .xinitrc file? Run this command and replace with the user you've created echo 'exec startxfce4' > /home/<username>/.xinitrc I also see that the guide states that you install slim-themes. Some suggestions point to editing /usr/local/etc/slim.conf and changing current_theme default to current_theme fbsd
Full answer by Alex: https://unix.stackexchange.com/a/668994 (CC BY-SA 4.0).
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