Get 5 of them in your inventory (less works, more doesn't as well).
Get a follower, preferably a "normal" one. I use Uthgerd and Faendal, ones like Serana and Cicero don't work as well in my experience.
Go to a place without much traffic. I like using Myrwatch, in tho lower center so things don't roll away.
Drop them one at a time (the reason I say 5 or less).
Tell your follower to pick them up.
Take them from your follower.
Repeat 4-6 several times, the more the better but I get bored after 10-20 loops.
Fast travel to another location with a full on loading screen with a background (you may have to go outside).
Fast travel back.
There should be duplicates where you dropped them. Tell your follower to pick them up and repeat steps 8-9 if you still want more. If you have enough, pick them up yourself to stop duplication.
It works best if you remove item clutter from the area, in my experience.