i think you could make this with tunisian. when it gets the the split, you could keep working half the stitches until both halves are long enough and then start stitching across the entire piece again at the other end.
МК Спицы "Пришивная" планка [ "This is in Russian but the photos are good. Attaching a knit placket", "Find and save knitting and crochet schemas, simple recipes, and other ideas collected with love.", " (Ideas from the Internet) / Crochet / Women