want to convert an existing image disk into a bootable image disk. What is the best way ?
Bootability is not an attribute that you can just add to a disk image. It’s determined by the contents of a disk. To make a bootable disk, you would need to run the Mac OS X installer on a hard drive or flash drive. Then you can add any additional files you want to the drive. Lastly, you would make a disk image of that drive.