Garment inspiration: An interesting, sleeveless cowl knit tube top one could wear with either end of the tube "up." It even has a halter-wear iteration. While labeled a DIY, it's just this series of s (Diy Ropa Patrones)
This is a pattern for a detachable Peter Pan Collar. The pattern can be easily adapted for different sizes by increasing or decreasing the foundation chain in multiples of I have written the patten based on my measurements to produce a collar aprox.