Well now that's ... hmmm.
I have one. Built out of my materials by Sportkilt. I used garment grade leather (Tandy Leatherworks were a tremendous help), took two full sides (approx. 4 feet each). Upholstery thread was used to hold it all together.
It's folded and sewed at the top and down to the hips but not "pleated" in the normal fashion from there down, it just kinda hangs that way.
You can ask James at SK how they did it, Robert at Rkilts has some nice looking leather kilts as well (I still want one of those too).
Good Luck.

CT - getting weller