Even with a false start (tangled my thread on the first try) and taking all the pictures, this project only took me ~30 minutes.
Step 1: Materials
You will need:
A length of ribbon or other trim material, approximately 1 inch wide
Needle and thread in a complimentary color
Closure of some sort (I used a 2 piece snap, other options would be hook and loop or a button and a button hole, or if you had self-stick velcro you could use that and skip the needle and thread)
A towel rod or other horizontal bar with some spare space on it for hanging your finished product
Wax for your thread
An embellishment for the front of your finished piece (a small pin, a cute botton, a flower ... whatever makes you happy)
Step 2: Sew on Your First Closure Piece
Keep in mind that your stitches will be showing on the outside. Be particularly careful to get all your thread pulled through evenly, and tie off as neatly as you can. Obviously the importance of this will vary with your chosen closure method and whether or not you choose to use an embellishment on the front!
If your ribbon has a pattern, or is lace like mine, you may need to trim a bit off the end to get the starting point you want; if your ribbon is solid, or you don't have a preference on where in the pattern you start, you can totally skip this part!
In my case, I knew I needed to sew through the large flowers to properly anchor my snaps, so I trimmed to a small flower.
Step 3: Measure and Sew Your Second Closure Piece
If you are working with matching points on a pattern or solid places in lace to sew through, make sure you take that into account when determining your position for the second closure piece.
Now you can go and sew on the second piece of your closure, the same as you did the first. This is the crucial one for neatness on the back side/tying off - if you don't use some sort of embellishment it will show.
Test your closure to make sure it snaps (or hooks or buttons etc) to your satisfaction.
Step 4: Measure the Final Length and Add Embellishment
I opted to trim in a V shape in the middle of a large flower so that the end wouldn't be stringy. You may want to measure a small bit extra and give it a seam at the bottom if you are worried it will unravel.
Now you can decide if you like the front the way it is, or if you feel it needs some embellishment over the stitching. I happened to have a small pin that I thought was cute, so I used it. You could also consider sewing on a "for show" button, or hot gluing say a flower or some rhinestones.
Step 5: Fill and Finish
Here is mine filled and with the towel on the rod ... I also store long hair ribbons by looping them on the rod :)
Hope this helps you organize your hair doodads!