(This guide applies to any Debian/Ubuntu based distribution)
For some reason (complexity perhaps) it is not possible to configure full-disk encryption and LVM from the graphical installer in the desktop edition. It is possible to select full-disk encryption but this only creates one filesystem (root).
I want to use LVM to allow me to have more than one filesystem without having to enter more than one password during boot-up. It is not impossible to install Ubuntu desktop (or Linux Mint as in this guide) with encryption and LVM but it does require a little more work.