There are third party scripts to accomplish this. I would look at https://github.com/saveriomiroddi/zfs-installer. The only reason I have not used it is that I had already written my own https://github.com/HankB/Linux_ZFS_Root. And in this case, better the devil I know. (I'm presently updating my script to follow the most recent instructions at https://github.com/openzfs/zfs/wiki/Debian-Buster-Root-on-ZF...)
ZFS-installer appears to be more mature and is seeing more effort than mine. Perhaps I should give it a try.