Create new EFI partition on Linux

1. Attach a new storage device or create a partition to use for the EFI boot files.
2. Create a new GPT primary partition and format it as VFAT.
3. Edit /etc/fstab on target system to match the new storage device: /boot/efi must map to /dev/sde1, where /dev/sde1 is the newly created EFI partition.
4. Reboot the system to let the system mount the new partition into /boot/efi.
5. Run grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUBNewHDD to reinstall the EFI files to the newly created EFI partition. bootloader-id will be displayed in the UEFI & boot menu.
6. Run sudo os-prober.
7. Run sudo update-grub.
8. Reboot the system and select the previously created boot entry in the boot menu.

Note: An EFI partition needs to be VFAT formatted and it cannot be run inside software RAID arrays. Hardware RAID does work though.