Dunno how he did it, but here's how I did it.

I should have taken more pictures of that process, but I was on a roll and didn't want to stop.
I found some solid core silver solder that was a bit thicker than the 3-hole MLS gasket that I had. Basically, I put the gasket down on the block, used a little rtv in the coolant passage, cut a small piece of solder to "bridge" the hole, i.e. the diameter of the circle, laid it on the rtv, then set the head on and torqued it down. The solder should crush and expand enough to seal pretty well. Plus, it's on the outside of the head and directly in a coolant passage, so I really don't think it will get hot enough to melt the solder.

What I might do before I start it up is to clip the part of the gasket that protrudes in the front, and try to fill that small gap with some of the hard-set type RTV, but I really think it should seal ok the way it is- if people are getting them to seal with a small piece of rubber then this should be fine.
Brendan