Yes, these have answered my questions. In fact, Ditter's tutorial is sort of the design I had in mind except I was afraid if I put the right sides together to stitch, I might have to press it open with the iron but I see she said you can just press it open with your thumb so that is ok. That is why I thought of topstitching them together (just folding edge under and stitching on top to attach it to the piece beside it).
Now I need to check a thrift shop for a couple old sheets.