Hi kjh,
As best I recall when I built my wife's WD12 hybrid a couple of years ago the stitches get tighted after the bottom and side panel are all joined together.
I couple things to know as a first time builder
1)  there is generally a good bit of trial and error  when tightening the stitches  while trying to get everything nice and tight and minimizing the gaps.  Don't get frustrated!  Just keep experimenting with the sequence and tightness in the areas your having trouble with.  You'll be struggling for a while in an area and then hit that specially sequence and it all comes together.  Wood is a natural product and can be a bit fickle at times.  Patience!
2)  it may not be an issue with the fourteen but I actually had a bottom panel severely crack about a foot from the stern while tightening stitches.  I found out later it helps to soak the panels with warm water in this area just prior to tightening.   After scarfing on a new end piece and using this soaking method I had no more issues.
Have fun with your build!
Dave

Dave recalls correctly.

First the hull and deck assemblies are individually completed.

Then they are joined together, Of course, on a hybrid there's a lot more work to get the deck assembly to that point.

Have fun,

Laszlo