Ohhhhhhh....I suppose just because I have a different way to do it I've just got to say something!
I use the big-big combo as lightingguy suggests but not threaded through the RD. Pull the chain tight, see where the ends match up, then add two links to that length and break the chain so it mates up correctly. As with most things where it's tough to undo a mistake, round up a link if in doubt.
My guess is that this way works also because when you add the two links, it's adds the necessary length to get that angle in the RD lightingguy was referring to.