how to mount by UUID without using /etc/fstab

From the manpage of mount.

-U, --uuid uuid
       Mount the partition that has the specified uuid.

So your mount command should look like as follows.

mount -U 1234-SOME-UUID /some/mount/folder

mount --uuid 1234-SOME-UUID /some/mount/folder

A third possibility would be

mount UUID=1234-SOME-UUID /some/mount/folder

Related