Instructions on how to add an overlay filesystem are very much welcome.
Creating the media
Creating UEFI-only booting USB live media is pretty straight forward. Just copy the files to your FAT-formatted USB drive. That's it!
1. Example via terminal
You can do something like the following if
604A-00EA is your USB drive and you already have
$ 7z x ubuntu-12.04-desktop-amd64.iso -o/media/$USER/604A-00EA/
You're done if you have only one partition on this USB drive, otherwise you need to flag the partition as bootable e.g. via
# parted /dev/sdX set 1 boot on
/dev/sdX would be your USB stick and
1 the partition number that should be used to boot.
2. Example via GUI
Mount the .iso-file and copy the contents over to your USB drive. Press Ctrl+H in Nautilus to display and copy hidden files as well.
Add the boot flag via GParted.
3. Example on Windows
- Same as above, just copy files.
Press Windows/Super+X, go to diskmanagement and check if the partition is marked as active.
Please stop using pre-WWI grade operating systems like XP or 7 for usability's sake.