The first cut is the deepest

Here's a nice exploded view of the kayak from the construction manual.  If you order the kit, it comes with all the pieces pre-cut. If you're building from plans only, you get to make them yourself.

 At $70 a sheet, you measure at least three times and cut once. The sides and bottom panels start out as straight rips. If you're working by yourself, 4X8 sheet product is not wieldy especially if you don't have the luxury of having a table saw set up for cutting panels, so to help hold the outflow to prevent the sheet from flipping up off the blade I nailed a support to the porch rail.

One other detail... the side panels will be made from the 9.5 inch wide blanks ripped on the table saw, and the bottom panels will be gotten out of the 11 inch wide blanks. But if you use your table saw to rip your plywood to make all four bottom panel blanks, you won't have enough panel left to make the aft hatch. Instead, you have to cut one of the bottom blanks with a jigsaw. Study the panel cutting layout on the plans (page two) and you'll see why. So after I cut two 9.5 inch blanks and one 11 inch blank from each 4X8 sheet I just did a quick and dirty layout of the remaining bottom panel (measured using the edge as baseline and added a half inch or so) and cut it with a jigsaw. Just to check, I put the full-sized aft hatch cover template on the remainder before I cut - plenty of wood left...