UEFI makes it easy to deploy ZFSBootMenu without a local installation. Most
UEFI systems will search for and run an EFI executable at the path
/EFI/BOOT/BOOTX64.EFI on a FAT-formatted EFI System Partition
located on any disk that the firmware is told to boot. This executable can be a
standard ZFSBootMenu release image or a custom, locally generated image. Almost
any modern system can be made to launch a ZFSBootMenu instance just by
inserting and booting from a minimally configured USB drive.
On a USB drive, create a GPT header.
Create an EFI system partition on the drive. The partition should be at least 100 MB.
Format the partition as FAT.
Fetch a copy of the ZFSBootMenu release image:
curl -LJO https://get.zfsbootmenu.org/efi
Save the resulting download as
EFI/BOOT/BOOTX64.EFIwithin the EFI system partiton.
Tell your system to boot from the USB drive.