Sew your pockets as per instructions or your preferred method.
Neaten each centre front seam with an overlocker/serger. With right sides facing sew the upper front crotch seams together, sew from the notch near the base of the front crotch and finish 6mm (¼”) before arriving at the “V” neck. The lower crotch seam is sewn later, after the in-leg seams are sewn. Press seams open.
With right sides facing, sew the front neck facing to the front neck with a 6mm seam. When arriving at the centre front keep the needle down and clip into the V of the facing to obtain a sharp point. Once clipped continue sewing along the other side of the neckline.
From the right side, understitch on the side of the facing close to the seam. Turn out and press.
Open out the neckline and facing and with right sides facing, sew one end of the open straps to the opened top edge of the front neck and front facing.
With right sides facing sew the armhole and armhole facings together with a 6mm seam, commence at the underarm and sew up the armhole continuing through the strap.
Pull the facing out through to the right side and understitch on the side of the facing as far as you can get. Neaten the remaining raw edge of the facing with an overlocker/serger.
Repeat sewing the back crotch seams together and attaching back neck facing (steps 3, 4, 5 on your construction sheet).
With right sides together and with the strap sandwiched in between the upper back, stitch across from the neck to the armhole, keeping the needle down, turn the corner and stitch the back armhole and back armhole facing together.
Pull out the right side and understitch close to the seam on the side of the facing.
Cut the elastic and stitch it to the inside of the back waist area, start by sewing each end of the elastic in place first then sew along the top and the base of the elastic stretching it as you sew. Sew a vertical stitch through the centre back seam and the centre of the elastic.
With right sides facing sew the front and back side seams together, start sewing at the edge of the armhole facings, sew through the armhole seam and continue sewing down the side seam through the under pocket taking care not to catch the pocket opening as you sew (please note I have used a different method to attach my pockets in this example). Neaten with an overlocker/serger and press towards the back.
With right sides together sew the back and front in-leg seams together and complete sewing the front and back crotch seams. Neaten with an overlocker/serger and press towards the back.
With right sides together sew the short ends of the leg facings together, press the seams open. With right sides together, sew the base of the facings to the leg openings matching the notches as you sew. Understitch close to the seam on the side of the facing.
Neaten the remaining raw edge of the leg facings with an overlocker/serger (or turn in once like I have here) and pin to the inside leg of the pants, once in place stitch with a topstitch.
Hand stitch the armhole facings and neck facings to the main body using a blind stitch and press your fabulous new jumpsuit!