Following the notches, fold the pleats towards the sleeve placket and sew your cuff pleats, with a foot width stay stitch.
Take one pair of your cuff pieces, and press the longer edge of one of the pieces up towards the inside by 1cm. You don't not need to turn the edge up for the other piece.
Lay the pieces on top of each other, right sides together and sew a 1cm seam all the way around the edges except for the bottom edge. The seam you pressed up in the previous step should be caught up in the seam. Ensure to keep your needle down and pivot at the corners.
Layer your seam allowance using the same method you used on the collar - Trim one layer away to half and clip the corners.
Turn the cuff right side out and give a press.
Take your sleeve, ensuring it is right side out. Then take your cuff, and with the pressed edge facing upwards, wrap your cuff around the opening of your sleeve. Pin the raw edge of the cuff to the raw edge of the sleeve opening. Make sure you carefully match the edges of the cuff on top of the edges of the edges of the placket. Stitch the cuff to the sleeve with a 1cm seam.
Press the sleeve seam allowance down into the cuff.
Fold the unsewn edge of the cuff over so it just covering the stitch line, pin securely into place.
Now you need to edgestitch the cuff onto the sleeve. I recommend doing the edgestitching from the top side for your cuffs as they will seen.
You can edgestitch the base of the cuff, leaving the top edges clean if you prefer. Here i have chosen to edgestitch the base, but do a 5mm topstitch on the top edge of the cuff to match my decorative topstitching elsewhere.
Repeat all the same steps for you opposite sleeve and cuff.