I used a freeform lace scarf kit made by Mokuba, the Japanese ribbon company. The kit is comprised of two pieces of stabilizer, one is see through (for the top) and the other is papery and sticky. Both are water soluble. Mokuba puts out two scarf kits - one with all the directions, stabilizers and yarns, etc. and one with only the stabilizers (alot cheaper). Since I had read about this technique before and I wanted to choose my own ribbons and yarns, I chose the kit sans directions.
I've seen in various stores that Sulky also makes water soluble stabilizers that can be used instead - the price of all the necessary "ingredients" is comparable if you opt for that. I think you have to buy some fabric adhesive if you use the Sulky stabilizer, since the stabilizer isn't sticky and the ribbons and bits won't stay in place if you don't. Make sure you get the water-soluble adhesive spray if you do use it. I've since ordered a bunch of pieces of water-soluble stabilizer from someone on the internet (can't remember who...) and have made two scarves for friends from that. I don't have pictures of them because my friends live in the Netherlands, and I don't!
My finished scarves are 50 inches by 8 inches. They are composed of bits and pieces of silk embroidery ribbons, eyelash yarns, regular sewing thread and other yarns and ribbons. I used up a bunch of hand dyed silk embroidery ribbons I had made long ago and had never gotten around to using.
You could get creative and use other stuff besides ribbons, like those little fabric yo-yo's or bits of plastic, or old credit cards or whatever. As long as you can "lock" the little items in place, you should be able to do it.
I consider these scarves sewn items since you must lock all the ribbons and yarns together by machine, sewing a grid pattern over everything.
What you do is lay down the big piece of water soluble interfacing, with the sticky side up. You are going to stick all the ribbons and yarns, etc. onto this sticky surface.
First lay down an outer border of ribbon - one that goes all the way around the border of the scarf. This is important because it sets the boundaries of the scarf, and is the first surface you will actually sew. You don't have to lay out an outer border but it gives you a frame of reference.
Once that is in place, you get creative and place all your yarns and ribbons on top of that.
When you are satisfied with the freeform patterns of ribbon and yarn that will inevitably emerge, you then place the see-through sheet of soluble stabilizer on top of the ribbons - this piece of stabilizer isn't sticky, but will adhere to the sticky stabilizer underneath all the ribbons. You can go ahead and pin through all layers with quilters pins, just to make sure everything stays in place.Here you are seeing the backside of the scarf with the papery stabilizer and a grid sewn in 1 inch blocks.
After that, you sew a 1 inch grid through all the layers, this will "lock" all the ribbons together.
Finally, you dunk the whole mess in water and rinse out the stabilizers - this takes several rinses, and hang your masterpiece out to dry.