I just made this with batting. When you're putting it together - before you sew - lay the backing right side up on a table. Put the top right side down on the backing - lining up the ends and one side. Cut the batting the size of the top. Place the batting on the top (I spray basted mine.) Pin the long side together. Then pin the other long side AFTER you have lined it up. Sew the two long sides to make a tube, then turn inside out. I had to trim the batting on the short sides before I folded them down and sewed them.
Make sense?