Mine are 12 - 18" muslin. After I use up all the space I add another piece of muslin to the top and back and practice again. I can do the layering several times before it makes the needle unhappy. The larger the piece the more realistic the practice. After learning how to FMQ one has to consider how to handle the bulk of the quilt, but you don't have to learn both at the same time when you practice on a reasonable size piece. Mine are trash later.