These feel INCREDIBLE on the feet, but are by far the hardest to
make. I'd suggest beginners make at least three rugs before
attempting one as even I have trouble with them if I'm not paying full
attention.
The reason for this is, the stretchy material tends to cause the rug
to "pucker up" if you don't watch how tightly you sew it (and my
friends like to joke that my rugs are so tight that they could
water!) On the other hand, if you add too many double stitches, its
UTTERLY unforgiving.
They are worth the effort, they feel indescribably wonderful on bare
feet. Should anyone ever want to pay me to make one though, it would
have a substantial surcharge over a normal cotton/poly rug.