Create the usb installer, boot from it, then choose, either another usb, or internal drive. to install too
It will tell you to remove the installer usb,
as long as you have the boot order set to boot from usb first, it will boot libre from that, all settings are made on the usb
if you want to go back to whatever was on the internal drive, just remove the usb.
I have been running LE from usb on my nuc for ages.
I have used yumi, it gives you a list of various distros, LE isn't one of them, BUT I think you there is an option to install using sys? (something or other)