comments about FlashBios page
following the procedure in
the resulting image is unbootable.
If you attempt to boot it,
freedos. pause there.
man (8) mkdosfs can not make bootable filesystems.
However the image can be made
with mtools (if target pc supports int13h floppy) and nasm.
e.g.(20Mib) mformat -C -t 20 -h 64 -s 32 K:
the resulting is bootable and can be written with dd to usb,
or boot with grub(2) (in bios mode)