The bottom of the quilt is thumb tacked on. I guess you could use attach velcro and then stitch the backing onto canvas leaders. Of course this is older than velcro and Ma-ma just had thumb tacks or small nails. So, tack the backing fabric onto the 2x2 boards,roll the 2x2's to fit the batting and top.
Batting and top are also tacked down then everything is rolled until the 2x2's fit the frame. There are four slots in the top of the frame so you have a few options.
My husband can easily copy and make this. I asked him to make some to sell in my shop. I guess it's not a bad idea, afterall. The design is simple, but that's part of it's beauty.