I made a cover for my sneak boat that I thought would make it through one season til I could make something better... Well, that cover has held up great for three years now.
All I did was buy one of those cheap $15 rolls of "leafy-flage" camo fabric from Walmart... bought a small bundle of mixed color raffia grass from Cabelas $10... purchased a fifty foot coil of brown bungee from ebay $5... and a small roll of green floral wire from Walmart $2.
I layed the netting over my boat, cut the outside to match the profile with enough extra to wrap under the widest points of the boat. I wove the bungee cord through the bottom holes in the netting and snugged it up under the rub rail. Then I cut out the cockpit area, leaving extra fabric to dangle inside the boat and hide any edges. Using the floral wire, I tied small bunches of raffia grass to the netting. Between the camo netting and the raffia grass, it looks pretty good... but now I also toss some local vegetation on top when I am hunting.
That black thing sticking out of the boat is just a 2x6 that I covered in foam to use as a backrest. I can sit straight up or use it to lay back and get lower in the boat.
One other thing I did was buy some cheap black foam (like a yoga mat) and cut it to fit inside the bottom of the boat. It quiets everything down, creates an insulation barrier between me and the cold water and also adds a bit of cushion. My butt sits on a thick foam cushion meant for turkey hunting.