If you use muslin, then the top layer will be quite a bit thicker. If you use paper, you need to pull the paper off before sandwiching the quilt. I think that hand-sewn seams may distort more than machine-sewn seams when tugging the paper off. It is recommended to reduce the stitch length on the machine so the paper gets perforated more and taking the paper is easier.
Another thing to remember is that the strings you add need to be a little longer than the background square. You will need to square up the block when finished.
Did you check youtube?