Once you've sewed the length of the strap, stick a safety pin through one end and begin to (slowly) guide it through to the other, turning the whole piece inside-out. Which will actually be rightside out.  Photo 5 of 13 in Storage Slings

Storage Slings

5 of 13

Once you've sewed the length of the strap, stick a safety pin through one end and begin to (slowly) guide it through to the other, turning the whole piece inside-out. Which will actually be rightside out.