All you need to know is how to use a sewing machine to straight-stitch and zig-zag... I'll explain everything else in detail!
I've got a few up for sale on Etsy... or you can just look at them as examples.
Step 1: Deciding on Size
Now, how long do you want your skirt? If you want it SHORTER than 30" long, take your hip size and divide by three. Round up to an integer. That is about how many ties you'll need for the body of the skirt. If you want it LONGER than 30", take your hip size and divide by two. Round up to an integer. That is about how many ties you'll need for the body of the skirt.
Step 2: Gathering Your Supplies
It's good to have a few extra ties. I recommend using only 100% silk or silk blend ties for them to hang the best.
You will also need:
iron and ironing board
presscloth (a scrap of cotton fabric will work)
source of electricity
water spritzer (filled with water)
tape measure (hopefully you've still got the one you measured your waist with)
ruler or straightedge
good sewing scissors
1/2" or 3/4" non-roll elastic a few inches longer than your waist size
all-purpose thread in the dominant color of the skirt (if your colors are schizophrenic, just use black or white)
non-bulky seam reinforcing tape/web (not shown in this picture, sorry!)
Step 3: Prepping Your Ties
First, take off the label with the seam-ripper, being careful not to rip the tie. There are three main ways these labels are attached-- the short ends sewn on; a knot in each corner; glue. If you can pick off the glue, or don't mind the residue, fine... otherwise discard that tie.
Next, see that the wide end of the tie has a thick stitch just below where the label was, and the narrow end has a similar one. Seam-rip those and tug out and discard the threads.
(SECOND AND THIRD PICTURES)
Step 4: Prepping Cont'd
Then you can unfold the tie and see the ugly lining, which may be stuck to the tie still with some threads-- pull gently to remove it, and then pitch it. Not the silky stuff (black in this photo), it stays.
Some ties will have a very, very sheer fabric under or above this layer that is actually sewn in to the point. Just cut it out with scissors close to that seam-- it's so thin it won't make a difference.
Step 5: Prepping Cont'd
You will want to iron the entire tie... when you come to those funny diagonal seams in the middle of the tie, you will want to press them "upwards," towards the narrow end of the tie.
This will help keep them from bunching up when you sew. If any are especially frayed in that area, after ironing, clip the loose threads and carefully apply a minisucle amount of Fray-Check to the edge of the fabric-- making sure to hold it away from the body of the tie as it dries.
Now go back to the wide end and the silky sorta triangular piece of lining. If it's fraying, clip the loose threads and Fray-Check it. Once it's completely dry, take the Stitch-Witchery (THIRD PICTURE) and tear off the right length to fit underneath that lining piece. Put it in position, making sure none of it is visible (or it will stick to the wrong things). Fuse it as per package directions (here is where your press cloth comes in handy), trying to keep the iron off of where you Fray-Checked. Note that some ties may have a deep V shape in this area-- you can either put your Stitch-Witchery in deeper, or tear off two pieces and follow the V.
How long did you want it again? Take that number and subtract five. This is what you will measure to cut, because most ties are between three and four inches measured vertically from the widest spot to the very tip, and we still have the waistband adding on about an inch of length. Lay out the tie straight along the ironing board, being careful not to stretch it. Align your straightedge or ruler below the widest area, corner to corner.
Place the start of your tape measure at that line, in the middle of the tie. Now cut the tie at the number you are supposed to cut at, being careful not to get the tape measure!
That tie is ready and can be put aside.
Step 6: Wait, You Want Me to Zigzag First?
This part is important-- remember the little funny diagonal seam that we pressed upwards before? Zigzag it.
Clip your end threads (it's just good loose thread hygiene, and is easier than trying to find them when you're done).
Now zigzag the raw edges of the tie, STARTING AT THE WIDE END, about half an inch below the end of the silky lining, or, in case it's coming loose (as it sometimes does) about half an inch below where it comes loose, but NOT below the widest point of the tie). When you get to the funny diagonal seam you just zigzagged, make sure it still points towards the narrow (cut) end of the tie!!!
Step 7: Designing Your Layout
You can pin tags with numbers to them to remember the order if it helps, or take a picture, or write down descriptions... whatever you want.
Step 8: Piecing Your Skirt
Start stitching at the wide end. When you are about to the end of the silky lining, take your seam tape and lay it along your seamline and stitch with it in place.
(SECOND AND THIRD PICTURES)
Do that for all but the last few ties. At this point, after every tie, you'll want to hold it up to yourself. When you think the size is fine, measure the top. It will need to be at least as large as your hip size if you've going to be able to put it on. Add more ties as necessary.
When it's perfect, press the seams open (it's easier to do this now than after it's done) and sew the first and last tie together, and press that seam.
Step 9: Attaching the Waistband
Press the waistband in half lengthwise, wrong-sides together.
Stitch the ends of your waistband together to form a loop.
With the skirt inside-out, pin the waistband, inside-out, to the skirt, matching dots, and stitch (do the seam tape the whole way around).
Press the seam UP towards the waistband.
Fold the waistband along where you pressed it before (dotted line in SECOND PICTURE).
Fold the raw edge under about 3/8" (dotted line in THIRD PICTURE) and pin to right side of skirt. You really want this folded edge JUST BARELY covering the seam from when you initially attached the waistband. Topstitch close to the edge, leaving about 1/2" to feed your elastic through.
Put a safety pin on one end of your elastic and feed it through the waistband, starting at the little gap you left. Make sure it doesn't twist. Pin both ends of elastic together when you're done and carefully try it on. Adjust elastic as needed. Sew ends of the elastic together-- I prefer to zigzag over it a few times. Stretch out the 1/2" unsewn gap and sew it carefully (or by hand).