If you create it correctly you should be able to create a flat surface.
Go into the layers properties and make sure all the layers are set to developable (check the box) then go under tools and select develop plates. This should develop the panels.
If they are really messed up, you will need to select sections of the hull and place them on different layers. If the hull is too rounded it won”t come out right any which way you do it. Boats designed to have developable panels are designed in a certain way, taking into account the limitations of using sheet materials. A round bottomed hull or even a round bilge hull is 99.9% not likely to be developable.