Start with a square (I think mine was 9")
Make a slice to one side of center, cutting the block into roughly 3/5 and 2/5.
add in a strip of fabric.
Press. Rotate the block a quarter turn, slice again, making 3/5 and 2/5.
Add in a strip of the same color. When joining the pieces, fold back the top a bit so you can line up the seams of your first strip.
Press. Rotate the block another quarter turn. Slice and add again. This time I put in a different colored strip.
For the 4th cut, I added in the same yellow, making it appear to overlap the moss green.
As you slice and add, be sure to keep rotating in the same direction and it will appear that your ribbons overlap in a spiral pattern.
Some slices can be a little wonky/angled, but be sure to match seams carefully and pin if you want your earlier strips to line up.
It's really not as difficult as it looks. Go ahead, give it a try!
My second attempt:
If you make any, I'd love to see them! add links to blogs/flickr in the comments~