Ok so i have 2 sleeves, and a front and back piece.
I'm now doing the neckband,
Using back-stitch, join reglan seams, noting that tops of sleeves form part of neckline.
With right side facing and using 2.00 needles, knitt up 79 sts evenly around nec, incl sts from stitch holders and working a button hole as before.
I have lied it out and think i can figure out how it joins, however confused I have looked on this site for back-stitch, and what is reglan seams?
Just use the mattress stitch for seaming. You can't join them 'seamlessly', you knit them them that way instead of in pieces. But you're done with that part, so all you have to do is sew them together.