You're going to need:
a mechanical pencil, or something with a blunt-ish end for poking with
a strip of metal for the parchment
something nice and sharp to cut it with
something not as sharp for shaping
a wastefully small piece of greenstuff
Right, first you have to cut a fringe into your bit of tin; five or six wouldn't hurt, making the last cut longer before cutting them all off in one piece-- these will be your parchments so make them as long and thin as you want. This is why you cut them first, observe;
If you expect to get them out of a pre-cut rectangle you'll have a fiddling time.
Once that's all done you can fold it in half if you want for a bit of depth.
Array the greenstuff across the tab which hopefully you left on the end. You see now where this is going... Do you know how to model chainmail? Here is a link to a basic rundown of the technique (not my video). We shall be doing that, only on a slightly bigger scale.
With the nose of the mechanical pencil (or your poking weapon of choice) poke holes into the greenstuff, pulling it out a bit here and there as you see fit and making sure they end up overlapping a bit. It's hard to explain, but practise should iron out what you aren't happy with; the shaping tool is then used to round edges and basically make the seals look like individual pieces.
Lastly, you can add plastic detail to the inside of the wax if you want. I suggest using the skull icons from the 6th ed vanilla marine helmets every man and his brother seems to have rattling about the bottom of their bitz boxes; they're the only ones I found small enough. Or you could waste a whole sangiunary guard pauldron and cut the goblet out of the primarch's hands and use that.
And that's that. All that's left is waiting for it to dry and giving it to whoever deserves it.
I had an idea of making occasional kitbashing tutorials and posting them; this was my first, would you care for more? Let me know if you found it useful.
Bye-bye for now.