How to stitch a French seam
A double seam that encloses the raw edges of the seam allowance. Allow for a total 1.5cm seam. Stitch the seam wrong sides together using a 7mm seam allowance, then trim to 5mm and press to one side. Press the seam back on itself along the seam edge, with right sides together and sew a second 7mm seam. Finish by pressing the seam to one side. Where two French seams meet, match the seam lines wrong sides together and lay the seam allowances away from each other to reduce bulk.