This small Howto is about setting up a USB stick to boot different iso files using grub's loopback capability. I only tested this on Fedora, but it should also work on other Linux distributions.
lsblk
This should give you a list of all your block devices. My stick is found as /dev/sdc
- we will use gdisk
sudo gdisk /dev/sdc
- create a new empty partition table by pressing
o