Piecing backs isn't hard, I do it often, mainly because I didn't buy enough fabric. Just start in the middle and build out. Or start on one side and build out. Just remember those seams, the more seams, the more issues you MAY have, not necessarily will have. The only trouble I have is when I hand quilt with multi-seams on the back. So my stitches are not perfect at that spot. See if you can find it, on horseback, at a gallop, holding a chicken! LOL Your quilt, your rules.