Thank you for taking the time to help me!

But why use the fashion fabric underneath? No one can see it. I'm so confused! See, my fashion fabric is white taffeta with black velvet flocking. If it's backed in the same fabric, it'll show through on the white parts any black behind. Can't I just use white cotton back there?

And can you tell from these directions whether that boning channel shows on the outside? I think it does...?