The instructions for the Whitlow robe suggest French seams for light to midweight fabrics and overlocked / zig-zag stitched finishing for bulky or heavyweight fabrics.
French seams are a great, durable seam finish option for light to midweight fabrics, particularly those that are prone to fraying. They are also great for sheer fabrics where you might be able to see the seam allowance through the fabric. Although they are more time consuming than other seam finishes, French seams are very satisfying and give a beautiful, clean finish without the need for a overlocker / serger.
a Pin the pieces you are joining together with wrong sides together. Stitch with a 6mm (¼in) seam allowance.
b Trim down the seam allowance by half (3mm / ⅛in). Be careful to not leave any threads along the seam allowance, as these can end up poking through the finished seam if you are not careful. Press seam allowance to one side.
c Turn the pieces so that the fabric now has right sides together and the raw edges are sandwiched in between the two layers of fabric. Pin another seam, enclosing the raw edges. Stitch with a 6mm (¼in) seam allowance. Press seam allowance flat to one side (refer to the instructions for the direction seam needs to be pressed).
