The Wardie cardigan is worked in pieces from the bottom up. When the front and back are complete they're joined at the shoulders and then the sleeves are worked from stitches picked up around the armhole. The shoulders are shaped at the back, with neat cabled decreases and the bound off edge of the front pieces wraps over the shoulder to join the decreased edge. This style of shaping is known as English tailoring and gives a beautiful fit and a neat finish that's often found on high end ready to wear knitwear.
If you're interested in knitting Wardie but aren't sure about the finishing here's how the shoulders and sleeve go together.
With the side seams left unjoined you can see how the sleeve is attached to the front and back armholes. The sleeve is to the right of this picture and the front is at the top. The shoulder line on Wardie is extended beyond the natural shoulder point, but not quite as wide as a drop-shoulder garment. Consequently very shallow sleeve caps are shaped with short rows.
Line up the outer edge of the top of the front (make sure you're joining the correct front piece!) to the safety pin on the back at the first decrease. Use pins or Cocoknits Claw Clips to join the pieces:
The back edge will be a little tighter than the front, distribute the fabric evenly.
Removing the clips one at a time as you go, seam the front and back together. If you're unsure how to join a vertical and horizontal edge like this there's a useful illustration here.
The completed seam:
The sleeve stitches are then picked up and knit along the armhole edge, from one side seam to the other.
Here's a great tutorial for picking up stitches on both horizontal edges (like the underarm bind offs) and vertical edges (like the rest of the armhole).
When all the stitches are picked up. You can see clearly in this image that the centre top of the sleeve doesn't line up with the shoulder seam, because the front wraps over the back of the shoulder.
When the sleeve is complete (and I find flat sleeves always go much faster than ones knit in the round, for some reason), the sleeve is folded in half and side seams are sewn in one: from the bottom edge of the body, up to the underarm and down to the cuff. The number of rows should match up perfectly, but I still find it helpful to clip everything together beforehand. Join these seams with mattress stitch.
If you're interested in English tailoring you might want to check out the Cocoknits Sweater Workshop which features a top-down seamless version of this construction method.