The Sailrite website is a fantastic place to go if you want to learn more about making your own cushions. I ordered the Sunbrella fabric and all the supplies needed from their website. I was able to sew the box cushions by watching their tutorial videos. I ordered new 4″ high-density polyurethane foam sheets and cut the foam with an electric knife, as instructed in tutorial videos.
The old cushions were not in good shape but we kept them so they would be used as templates for new ones for the dinette and the bed area.