I found this video on how to duplicate items in Minecraft: https://youtube.com/watch?v=9Fr4NfHd9Ik
MC-101512
Duplication glitch in the End
Resolved
Invalid
0
(Unassigned)
Unconfirmed
Minecraft 1.9.2, Minecraft 16w14a, Minecraft 16w15a, Minecraft 16w15b, Minecraft 1.9.3 Pre-Release 1, Minecraft 1.9.3 Pre-Release 2
Retrieved
That video is from 15w45a, which is a outdated snapshot.
It's likely that the "flying kick" has already been fixed (not sure, not really bothering to look for such a ticket at the moment.)