The great kilt was simply 5 or 6 yards of tartan cloth wrapped around the wearer and secured with a belt. What I did was just buy 5 yards of tartan cloth and wrap it myself. Here's a good page explaining how to wrap a great kilt.

I've worn this type of kilt out and about and I can say that wrapping it each time is a bit of work and the extra cloth above the belt can be difficult to handle. A friend of mine suggested donning the great kilt, pinning the pleats in place and then sewing them down to keep from having to re-pleat the kilt each time you put it on.