I made a cover for one of the large hot pads (insulbrite, knitted wool, cotton batting) I made a while back using four different fabrics. It is removable for washing and also reversible with four different options. The pad measured 11" x 17". I cut my rectangles to 11.75" x 18.75" and sewed a 1/4" seam when I was putting it together. I left an opening on one side and turned it right sides out and then hand stitched the opening closed. I top stitched both edges and then added two more rows of stitching to keep the cover integral when washing it. We have such beautiful fabrics available for sewing!!
Therese

