Neaten the outer straight edge of the frills by overlocking/serging then turning in once and stitching, alternatively you can double turn and sew a narrow hem.
Sew a large gathering stitch between the notches on the opposite edge, draw in the gathering stitch to the measurement between the notches on the front and back armhole. Press and put aside.
Overlock/serge each centre back seam. With right sides facing sew the centre back seam from the hemline up to the notch indicating the back split opening.
With right sides facing sew the back and front shoulder seams together.
With right sides facing pin the sleeve frill to the armhole between the notches marked on the armhole. Once in place stitch on.
Sew the shoulder seams of the front and back facings together, sew the small seam at the base of the centre back facing, stitch from the base of the facing up to the split notch. Overlock/serge the bottom edges of the facing.
With right sides together sew the neck facing to the neck of the body, turn out to the right side and understitch close to the seam on the side of the facing.
Make up the small back loop by sewing along the length of the rouleau and turning it out to the right side. Sew the loop to the left back neck at the top of the split. Stitch the loop facing inward as when the facing is stitched to the split and when turned out the loop will face in the right direction. The loop is to be a size to match your button size. In this instance, I have used a small amount of elastic instead of making a rouleau loop.
With right sides together sew the back split opening to the facing split. Sew from the neckline down from the neck to the notch, repeat for the opposite side.
From the inside pin the front armhole to the armhole facing sandwiching the frill in between, once in place sew from the front side seam up to the shoulder seam. Then repeat by sewing from the back side seam up to the shoulder seam. Turn to the right side and understitch to the facing on the side of the seam.
With right sides together sew the front and back side seams together, start sewing at the hemline, sew up to the armhole and continue sewing the side seam of the facing, turn the facing to the inside of the dress and catch the facing down with a stitch.
Blind stitch the hem of the dress to your preferred length.
Sew a button to the right side of the neck.
Press your masterpiece!