I work with a lot of panels at the LQS for shop samples...some are small squares, others 2/3 yard cuts. My current project is a 1 1/4 yd cut. We do not wash and dry panels. Like feline says, find the design center and cut as she suggested. I do this all the time. Often times narrow borders known as coping strips, are added to the preprint and then cut to an overall uniform size. Not too long ago I had a flannel panel that was "not square". I followed the instructions on the pattern using the coping strips and trimmed to the specified measurement and finished piecing the borders. When all quilted and bound, all was fine.