Take one piece of centre back waistband. This will be the inside waist layer. Snip the pocket opening notches at the inside LHS side seam, fold back and topstitch the pocket opening edge with zig zag or twin needle.
Take the pocket bag and align with the seam opening, topstitch around the pocket bag curve.
With right sides together join the side panels to the centre back waistband. Take care pocket opening is not caught in the side seam. Topstitch if desired towards centre back.
Join the other side of the side panels to the centre front waistband. Repeat for the outside waist layers. There is no pocket on the outside waistband.
Check the finished waistband measurement and cut elastic to the same length or your personal length. Overlap each end of the elastic by 1.2 (½”) and stitch closed. Your elastic loop will now be 2.4 cm (1”) smaller than the finished waistband.
With right sides of the 2 waistbands together joining the waist edge with the elastic. Stretch gently while sewing to ease the fabric to the elastic.
Turn out the waistband to the right side and topstitch the elastic 6mm (¼”) from the seam on the inside.
LEGS & POCKETS:
With right sides together join the centre front crotch seam. Topstitch to one side if desired (not pictured).
The gusset will be double layered. Place the 2 gusset panels together and treat as one piece, then with right sides together sew one side of the gusset to one side of the back crotch, turn the seam towards the side seam and topstitch if preferred.
With right sides together sew the 2 centre back crotch seams together finishing at the other side of the gusset. Turn the seam towards the side seam and top stitch along the back crotch seam and through the gusset if preferred.
Fold and hem the side pocket edges with zig zag or twin needle stretch stitch. Optional clear rubber elastic can be sewn to inside of the pocket hem to hold the edge. Place the pockets on top of the side panel as shown below and tack at pocket opening and lower side seam point.
With right sides together attach the side panel to the main back panels around the curve. Match the centre back pant seam to the CB yoke notch. Turn the seam downwards and topstitch if preferred with a stretch stitch.
With right sides together join the front and back in leg seam. Start at one leg opening, match notches and finish at the other leg opening. Note the centre front crotch seam will be in the centre of the gusset. If topstitching, turn the seam towards the front leg and top stitch with a stretch stitch.
Turn the garment inside out and with right sides together join the front leg seams from waist to hem. Make sure to sew both layers of the side panel and pocket. If top stitching, turn the seam towards the centre front and topstitch with a stretch stitch.
Fold the waistband over so the elastic is inside, and with the 2 cut edges together join to the right side of the main body. Match at side panels and CF/CB. Stretch slightly to ease the main body to the band. Turn the seam down and topstitch with stretch stitch.
The garment has a raw hem. Secure the leg seams 1cm (1/2”) from the cut hem edge with bartack.
Give the garment a final steam press and finish.