Yes, I understand what you mean

I was making a silly joke based on a very old poem about fleas. Which no-one found funny

Except me

when I made monkey fists, I did a fig8 knot, then did a 2 bight monkey around that, then a 4 bight monkey around that. You might find 3/8" (about 9mm) rope easier than 1/2" (12mm).
I should also tell you to do a search, because there's lots of information about this on here already:
http://www.homeofpoi.com/search/search.pl?Terms=monkey+fist&x=0&y=0(bight is a term for what you're calling ply or fly)