Tutorial: www.justanotherhangup.blogspot.jp (Gathering Fabric & Muslin Pillow Tutorial - also contains a link to the tutorial for tattered muslin rosettes)
As you can see in the photo, I did not use muslin but a cream cotton with metallic gold stars. I also made an envelope-style back and layered both with Pellon fusible fleece. I have not yet made the actual pillow so the above photo is unstuffed. I hand stitched the rosettes instead of gluing them and then hand stitched them to the pillow. The finished size is 14" x 17".