This jacket has no collar, as all the focus is on the neckline. Finishing the neckline on the front pieces of the jacket is not a problem, as the facing extends up to the neckline. It can therefore just be sewn, turned, then pressed closed.
I had to make a decision regarding how to finish the back neckline. At first I though I would just be able to proceed as I would any normal jacket (with a collar), by turning down the top cloth and cross stitching it down to the canvas; then, folding the lining up and slip stitching that into place. However, upon much consideration I realised that the absence of a line of firm stitching would mean that the neckline was not secure and could stretch out of shape. I therefore decided to cut a facing out of top cloth, fairly wide (2") to allow for the fabric rising up when the jacket is worn, allowing a glimpse of the inside, so that top cloth is seen and not lining.
Upon further research into men's jackets, I discovered that some jackets (depending on the brand/tailor) do in fact have a crescent-shaped cloth facing below the back neckline, even with a collar. This has served to confirm my idea of securing the neckline as a good one, as it is done by other practitioners.