The 15th layer of planks must now be glued to the bottom plank, and to each other, since there is no more stem material.  This will create the bottom portion of the boat.  They also have to be cut and shaped a different way in order to fit correctly, as compared to the planks on the sides of the canoe.  This is another reason why the bottom plank is glued to the forms, so it stays straight when these planks are applied.  Again, all rough edges will be sanded away, but it's best to fit them as closely and as snugly as possible.