A very good idea is to start pretty far back in the "Mod Request for More Ship Types Thread" (as recommended) and read your way through it. A lot of the progress made in shipbuilding originated in that thread, although some was done through PMs. Most of the early information has been rendered obsolete through newer versions of Pack3d, new methods, etc., but you should still read the early posts to get an idea of what to do. But don't start building until you get some newer info. Also, search for older threads (especially those which included discussions by Sergbuto, Iambecomelife, or myself).
And make sure to have Pack3d, of course.
I don't think anyone mentioned it here yet.