I'm not sure how its done, but after looking at it I think I know how I would try it. I always like to leave my options for handquilting open so I know I wouldn't add a muslin backing or fuse it all down. Maybe if you take long strips of fusible and make skinny strips of it to layout and then fuse the very ends to to make the first set of rows it would stabilize enough to weave in the other direction. I just would make the lengths of fabric long enough to be able to cutoff the ends. Then sew the binding on and cut off off the longer ends with the stabilizer on it and continue in the normal fashion.