1. To make a UbuntuMate 16.04 Raspberry Pi SSD I downloaded the image from here: https://ubuntu-mate.org/raspberry-pi/.
2. Then I used the commands below to unzip the image.

sudo apt-get install gddrescue xz-utils
unxz ubuntu-mate-16.04-desktop-armhf-raspberry-pi.img.xz
sudo ddrescue -D --force ubuntu-mate-16.04-desktop-armhf-raspberry-pi.img /dev/sdx

3. Then I downloaded the Win32Diskimager to a Windows PC and used that to install the image to my SSD card.