I've done similar by digging a small, tight hole just deep enough to set the esbit down in with about a finger's width around it. I line the hole with a little aluminum foil, letting the foil stick up past the hole a ways. Then sit the stove down in it and light the cube. I flare the aluminum out at the top of the hole so I can sit my pan inside it. I don't bind the aluminum too tight, just enough to duct the heat up around the pan and allow enough draft (a small straw stuck down through the aluminum might help draft it better. I can get a good boil going on two cups of water this way fairly quick, though I haven't timed it. The water boils before the esbit is consumed.

I wish I had a picture of it. Hopefully you get a good sense of what I am talking about. I came up with this after thinking about how a dakota hole works.