We've always ironed freezer paper to the back of the blocks to stabilize them & have people sign them with pigma pens. Then heat set the ink before ripping away the freezer paper, then sew blocks into quilt. REMEMBER to draw a washable outline for people so they don't write out into the ¼" seam allowance.... you might want to put at ½" border allowance so the fancy swirls etc. aren't cut off.