I am making a practice OBW and used the left over hexes to piece the backing. Except for a seam to join the widths of fabric, I've never pieced a back before. I know that it's not going to be perfect, but I wanted the back to be as centered as possible, so I took a thumb tack & stuck it thru the center of the back, so when I layed the backing on the table, the point was up. I taped it down, put the batting on it then I found the center of the top & used the thumb tack to match it to the center of the back. Seems to have worked well. Is there a better way?