The correct method for finishing a round neckline is to cut the facing strip at a 45° angle to the selvedge, commonly known as cutting on the bias.
This approach is preferred for the following reasons:
Enhanced Stretch and Flexibility: Bias cutting enables the fabric to stretch and curve more readily, crucial for neatly finishing rounded neckline edges.
Achieves a Smooth Appearance: The bias cut allows the fabric to adapt better to the neckline's natural shape, yielding a smoother, more professional result.
Improves Drape and Flow: Fabric cut on the bias exhibits a more fluid drape, contributing to a tailored look that contours the body seamlessly.
Broad Applicability: Beyond necklines, this technique is frequently employed for armholes and other curved sections in garment construction to achieve crisp, refined edges.