Download our flat bottom boat design for the extreme flats 20, a light weight, quiet hull with low freeboard. buy flats boat plans and more at bateau.com!. Boatplans.dk – online free and inexpensive boat plans for canoes, small boats, sail boats, motorboats and powerboats. download boat plans right away. – boatplans.dk. It takes only a little time, money, and effort to build one of these rugged – yet simple – flat bottom skiffs. every model includes details for two bottom profile shapes..