Thanks to these users for the various guides on setting up different desktop environments on FreeBSD.

kdefreebsdKDE on FreeBSD 10.2 by
http://www.ostechnix.com/how-to-install-kde-in-freebsd-10-2/

KDE on FreeBSD 11 by
http://fosskb.in/2016/02/17/installing-kde-4-desktop-on-freebsd-11/


matefreebsd
MATE on FreeBSD 10.2 by
http://www.ostechnix.com/install-mate-desktop-freebsd-10-2/

MATE on FreeBSD 11 by
http://vpierre.it/installing-mate-desktop-on-freebsd-11/


gnome-on-freebsd
GNOME on FreeBSD 10.2 by
http://www.ostechnix.com/install-gnome-desktop-environment-in-freebsd-10-2/