If you connect a valid boot volume the machine should seek and find it on its own (give it time... up to 10 minutes). Part of the POST (power on self-test) is to locate a boot drive... that's why a flashing "?" shows on the screen... or a folder with a ? or a bar through it... that is the EFI way of telling you "I can't find an OS to use to boot this box".
You might want to disconnect the failed drive, and any other peripheral save the boot volume be it optical disk, thumb drive, external drive or target booted Mac computer.
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