Here I am marking up a high spot at one end.
The bowsprit tapers fore and aft - top and bottom, and both sides.
We are provided with one pattern for the top and bottom faces, and one for the side faces. the first thing to do is to clamp the first pattern to the top and then the bottom face, and to mark in the tapers.
I tried using a long blade in the jigsaw but it was ineffective. In the end I used a sharp panel saw and cut them by hand. It was no trouble.
Then the tapers are planed flat and true, as in this pic.
When all four tapers are finished, the second set of tapers is marked up. Here the second pattern is clamped to the sides of the bowsprit and the tapers are pencilled in.