If you are in trouble with preparing your slides, you could use the template attached to the page. It contains a LaTeX source file that you can modify to create FreeBSD-themes slides. It uses the Beamer class which is an easy-to-use extension to LaTeX for making presentations. You can easily install it by the following command (as root):
# pkg install texlive-texmf
This will install Beamer and pdfLaTeX that can be used for compiling the sources to produce the desired PDF file.
$ pdflatex my-presentation.latex
Or you can use the LibreOffice / OpenOffice template (contributed by BaptisteDaroussin).
A few rule-of-thumbs when creating slides: