Ok.. so there seams to be different ways to do this. Some pad everything with landau and some glue straight to the substrate. By the looks of this picture it looks like he uses no padding and it looks amazing to me. He obviously skives the leather but my question for everyone here is what is your preferred method to cover dashes, plastic seat trim, door panel, etc.
I usually skive the seams in a sloped way. For the first closing sewing I use a thin needle 110/18 to avoid big holes and a 'thread clashing view'.
Master trimmer Brent Parker shows us a nice way of approaching 'french seams' on dahsboards and other pieces which do not suffer tension. http://www.thehogring.com/2012/09/13/how-to-sew-a-seamless-french-seam/
Also notice how the upper french seam is located back from the edge of the plastic. Most french seams would be more forward so that the initial stitch is located at the very edge of the plastic. By recessing it back it looks much cleaner. Very cool technique!