I kept the foam pad from the old cover. Then cut a piece of fabric a few inches larger than the board. I hemmed the fabric and inserted elastic on the narrow end. It will be complete when I add ties or elastic to keep the sides down.
I also made a new cover for my sleeve size ironing board. The old muslin cover was brown and dirty. I used two layers of quilt batting for padding. For this ironing board I inserted elastic around the entire cover.