French seams are sewn twice, encasing the raw edge within the seam and creating a very neat, delicate seam that is ideal for sheer or lightweight fabrics.
With wrong sides together, pin the corresponding pieces. Using a straight stitch, sew a seam at a 3/8” seam allowance.
Trim the seam allowance in half.
Press the seam allowance flat and to one side.
Fold the fabric with right sides together.
Stitch again, this time using a 1/4" seam allowance, encasing the raw edge.
Press the seam to one side to finish.