How can we make a bootable image with a bootloader by way of no emulation option using mkisofs, or similar good tool else, along with directory tree of a Linux OS in a HDD partition in order to have that all archived into an image/ISO file from which we copy into USB disk (burn into CD for other term) and have that linux OS (in that mounted partition) run directly (live) from that USB
Tried grub-mkrescue (cannot be converted to hybrid by isohybrid) to no avail:
https://www.gnu.org/software/grub/manual/grub/html_node/Making-a-GRUB-bootable-CD_002dROM.html
Please give clear guide, mini tutorial in clear step by step
https://www.linux-live.org/