This howto will show us how to manually create a bootable USB (flash) drive using the EXTLINUX bootloader.
Unlike SYSLINUX who installs on FAT formatted drives, EXTLINUX can be used for EXT2/3/4 and even btrfs formatted drives.
EXTLINUX is easier to use than GRUB.
Why use the EXT2 filesystem? It is recommended for flash drives as it is a non-journaled filesystem so the write operations are reduced compared to other journaled filesystems.
See http://en.wikipedia.org/wiki/Ext2 for more info.