Barb is clearly the master here, but my take has always been that it's okay for the raw edge of the waistband to show inside the kilt at this stage because the lining is going to cover it when it gets sewn in.

I've always done the following:
1) Fold edges in (at an angle where - using your pictures above as a guide, the bottom is farther left than the top - so that what's folded now will be inside the edge of the apron when folded down)

2) Fold top down once.

3) Sew it down.

4) <other steps>

5) <Sew in lining which covers the waistband raw edges>




Edit: Barb is also the master of typing faster and more concisely.