This was fascinating to listen to, so I thought I'd share the insights with WoW Insider readers. This is not verbatim quoting throughout, as I simply can't write that fast, but it covers the raid-making process as they described it.
How do you make a raid?
You start with the lore. Ion and John talked us through the process of making the Firelands raid, so they began from a set of conditions. As Ion put it, "We consider what the idea is. What is this raid going to be about?" So they sit down with the encounter design team as well as the game producers in a meeting room and talk it out.