I cut the pattern pieces the same sizes.
With outer fleece on top, pin the outer fleece inward between elastic marks only.
Sew along outer fleece with your normal seam allowance.
Tack elastic to elastic markings and trim excess inner fleece or flannel.
Now you can turn. I am a big pinner. I pin around elastic to make my casings. That way I *know* I won’t sew through the elastic.
Then… you’re ready to topstitch….And the diaper is finished