It fits right over the top of a tissue box.
I just measured the sides and cut pieces of fabric, adding a 1/4 inch seam allowance for each side. Then for the top, I measured and added a 1/4 inch seam allowance for each of the edges that are on the side and for the middle 'slit', I added a 1/2 inch seam allowance and sewed this first, then I pined each end of my slit and treated it just like I would a side and sewed, wrong sides together. When that is all done, just go along your bottom edge and sew 1/4 inch seam. Now turn right side out.
I bought a yo-yo maker and thought adding one yo-yo to the top with several stitches just made it pop. It is late and I am tired, so please let me know if you have any questions.