I think...cut waistband from fabric and this foldable waistband stuff MIL has given me, iron shiny side onto waistband, stitch to skirt along first set of holes, fold in middle, tuck in top edge & sitch again?
But I'm not sure & have never used anything like it before
I think it is called petersham although I have never used an iron on one. It is useful when cutting a waistband on the bias but would work equally well on the grain. I think your suggested way of using it is spot on. Good luck
Its Vilene Waistshaper. You iron on to the waistband with a dry iron, the perforations allow really sharp pressing for a good clean fold.
Apply the interface then when you apply the band to the skirt body use the first perforations as a stitch guide. Fold in half and press, then turn in and press the last small fold and finish your waistband.