Welcome from Ontario, Canada. It depend on what kind of crushed velvet it is. You can iron a fusible stabilizer to the back of the crushed velvet if it can take the heat of the iron. You can also surround a crushed velvet square with woven fabrics on all sides, to help stabilize the square. Many Crazy quilts from the Victorian age used velvets, satins, lace, taffeta and embroidery.