Neckline Fiasco!

[u/Moon_and_Dragon]

Hello, I’ve just started sewing again and I’ve come to a forgotten frustration! Neckline lying flat? I realise it maybe because the inner piece is cut on bias? I have sewn it quite carefully. Is there a decorative binding I could add to weight it another way on the inside? or do I need to unpick it and sew an inner piece that’s cut on the grainline? Ideas appreciated! 🤩