Boat plans for the 13 this 13′ flat bottom skiff is a real workboat. it is so easy to build that you can build it in a day (maybe add a few days for fairing and. Flat bottomed swamp boats: three boats of ancient design. free boat plans and building instructions. published september 12. 2008 last updated september 24. 2008. Links to dory boat plans, many free dory boat plans, boat building information including plywood stitch and glue..