This is the steek of the right sleeve (on the right as worn). I had sewn along the centre of the six steek stitches with my sewing machine, i.e. on top of steek stitch number three and stitch number four. I am not sure how easy this is to see in the photo, The loose threads at the bottom may be the most visible bit.
Again, I put in four sewn lines keeping the line to be cut in the centre - these are about half a knitted stitch's width apart. The knitting needle sits at shoulder height, the bottom of the photo shows the cast on steek stitches - these will get folded inside and sewn down by hand and become facings.
Cutting the garment open between the middle two sewn lines:
I then grafted the shoulder stitches closed and began to pick up stitches for the dolman sleeves from a column of knitted stitched three stitches in, i.e. not inside the area of the steek stitches but the last 'proper' stitch either side (the three steek stitches need to remain as they are so they can be folded inwards). I then knitted these picked up stitches off together with the live stitches kept on waste yarn at the bottom of the armhole to make the second sleeve.
I also machine sewed the four stitch lines down the centre of the cardigan for the front opening but I haven't cut this open yet. I still have to knit the neck facing but will have to cut the front opening first to ensure I pick up stitches in the correct place and also so that the neck band will look okay.