You are supposed to boot the relevant version of MS-DOS (I know, chicken and egg... I'll get to that in a minute) and use
SYS A:
to put the needed boot files in the right spot. That is assuming that the disk is already formatted. Alternatively, could use FORMAT A: /S
That being said, there is often another way to get this to work. (I did a bit of research on this years ago when I considered writing a multi-version SYS program. But I didn't do that, and what I remember now may be quite old...) Often the trick was just getting IO.SYS at the first part of the disk, and MS-DOS.SYS might be required to be the very next file on the disk. The precise details varied over different versions of MS-DOS.
Using floppy disks may be easier than hard drives, since hard drives had MBRs to work with. But I think this old version of MS-DOS doesn't really support hard drives anyway, so definitely plan to be using floppy disks. (Or, since you said you're using VirtualBox, images of floppy disks.)
I suspect that using SETVER, and running MS-DOS 1.0's SYS from a newer version of DOS, might be helpful (if you're adventurous enough to keep trying ideas that may not work).
You may specifically wish to look for information related to the "boot loader" functionality of the operating system.