To answer your original questions (and accepting that, as Tug Fanatic says, there are 1001 ways to do this), this is how I did mine, almost entirely from stuff I already had. Sorry, no photos as I didn't take any!
The sides were from 6mm ply. I made sure the straight edge (deck line) was really straight then cut the shape out on my bandsaw. I then fixed the two sides together with double sided tape and used my drum sander to sand down to the pencil line, giving two identical sides. The bow and transom were 1/2" thick solid timber, glued and screwed in place, giving an empty, Springer-shaped box. The bottom I made from 1/8" thick 1/2" wide balsa planks fitted across the hull, not lengthwise, glued with superglue. As I said, just stuff I had to hand. This was then covered with glass cloth and epoxy as I didn't think the balsa would take the rough and tumble a boat like this is likely to get. Then the rudder and motor get fitted. Then a 1/4" square piece around the inside to take a 1/16" ply deck. Your access through the deck will depend on where your drive and electric bits are positioned, and the size and shape of your superstructure. Not sure how much more detail you want at this stage?
Enjoy your build.
Greg