I just took the old cover off, and used it for a pattern. I sewed 3/4” bias tape loosely to the edges, and ran 1/4 inch elastic inside the bias tape. Much easier to wash than the ones with the ties. I now have two so I can use one and wash the other. I did use the idea of 1” gingham for the second one for keeping lines straight on the second one, the first is just stripes. Both work great. I have two layers of 100% cotton batting under the covers.