If your are going to send inside your country
the best is still a small letter size padded envelop
as for crossborder it is different
padded envelop may ask signature
and even your addy the bastard
the coin holder is the best with a cheap
dollor store hose washer and a stapler.
you can buy them cheap online
Myself I put the seed inside the washer
and put a small piece of painter tape
on top so they don't move. (I seen postal
shaking envelop we don't want that) then
staple the 3 side.
in a small envelop you can put 3 side by side of those
just put the 3 and tape them to a normal paper then
wrap the sheet around . I also add a piece of cereal
box carboard on each side .
Last thing is to make shure its not over wheight according
to your country fare for the stamp.
If you ever ask me for seeds that how I ship them