How to boot from an image on a local drive ?

Hello,
It may be obvious or maybe an uncommon request but
how to boot from an (ISO) image located on a local disk drive ?
All info I found are about network boot but what about boot from local data ?
I cannot find a working syntax using sanboot nor chain. I can boot from
a drive (boot sector) but not from an image file on that drive.
All help will be much appreciated.
Thanks,
Ruymbeke