I am in the process of finishing a Great Auk and it is my third kayak build. I sanded and glassed the glassed the hull before flipping the boat over and building the deck. I do this because Nick recommends it both of his books, and found it works well for me.

Et is correct in pointing that seasonal relative humidity changes can cause the hull to close up like a taco shell or spread out. But this is easily taken care of with three spacer sticks.

Here are the keys to a first rate glass job. You can get the epoxy and glass technique here from Nick's or Bob's books. But more importantly: pick a weekend where you don't have to go out of the house for more than three hours. Line up two or three PITA, honey-do projects that don't take too long (fix the loose hinges on the kitchen cabinets, replace the bathroom mirror. nail up that last piece of baseboard in the bedroom), absolutely NO painting, plumbing, or yard work. Completing the honey-dos will give you the proper amount of time between epoxy coats, and trick the Mrs. into thinking that you are actually useful.