Okay, here's what I've learned after dicking around with these things for a few weeks...
The box-pleats use fabric at a 3-to-1 ratio... so if you want to box pleat 9' of organza, you'll need 9 yards (18 feet!)
Sue's seem to be mounted on some black twill tape, but I just used 3/8" grosgrain ribbon. I don't recommend satin ribbon; the organza will slip and slide all over that.
Materials:
1 10-foot strip of twill tape or grosgrain ribbon
1 9-yard (18-foot) strip of Black Organza (10" wide)
1 8-yard strip of Red Organza (10" wide)
1 8-yard strip of Yellow-Green Organza (10" wide)
2 WOF (Width Of Fabric) strips of Black Chiffon (10" wide)
2 (or 4) Black Tassels
Black Serger Thread (and obv. a serger)
If you don't mind piecing your organza together, you can just buy 2-yards and sew the 10" strips together to make one long strip.
Prepping the Fabric:
I cut 10" wide strips of the Organza and chiffon and serge all the long edges. If you want to use a rolled-hem foot on your serger, you may want to cut your fabric strips 1/2" wider to accommodate the hem (1/4" each side). I don't bother to serge the short edges, but you can if you want.
Getting Started:
I fold about 1" of the ribbon up to make a loop for the tassel. Some tassels have stupid-long loops for hanging, so I shorten those to about 2". I box-pleat the chiffon to each end straight down the middle - just sort of a loose pleat-as-I-go technique. I can see the ribbon through the chiffon. Make sure you attach both ends of the chiffon to the SAME SIDE of the ribbon! My pleats average about 1-1/4" deep.. back and forth alternating their direction (that's what makes it a box pleat). If you prefer you can pleat them all going the same direction and it should look beautiful, too.
Pleating the Organza!
Continue to attach all layers on the same side of the ribbon. This will help with the twist when it's hanging.
I attach the red first... slightly overlapping the black Chiffon ends. Not all of the boas have all of the colors running the full length, but I prefer to keep it simple and just go all the way across. Then the green/yellow - which I started and ended a little further in from the red. Then the black I started about 6" from the beginning of the ribbon - it overlaps a lot of the Chiffon.
You absolutely want to do the black organza last because it's the hardest to see through. You need to be able to see your ribbon/previous stitch line on each successive layer. It can be a little tricky with the black on top of the black ends. Just go slowly and keep your pleat layers spread as you work.
Commissions:
If you decide you'd rather just buy one I'd be glad to make it for you! Based on the materials I currently have available (see top photo) I am charging $125.00 (materials + labor).