HOWTO safely unmount remove USB zfs sdcard

[Russell L. Carter]

Greetings,
I can easily create a ZFS filesystem on a USB sdcard,
but I have not yet found the recipe for safely unmounting
it and then mounting it on another 12.0 FreeBSD system.

Ideally, the answer is just a google search away, but
alas, that has not turned out to be the case.  Yeah,
I suck at google, evidently.

Can anybody help?

Thanks,
Russell