My first projects were all from somewhat rounded or preshaped stocks.
Then when U had my own tree wood I went totally from the plank, squared.
Everything as far as drilling holes straight and trued were so much easier, and the results so much better I now leave everything square or at least some areas flat and square as long as I can.
I think that is why most preshaped stocks I have seen still have square and flat areas, to aid the builder.
It was alot tougher for me to work the stock into shape I wanted, but in the end, worked out just fine. And for me at least more of a sense of accomplishment.
But to each his own.
I am not very good at most of the aspects of gun building, but I am purty decent at hole locating, drilling and pinning.
Finally, I leave my pins long so I can just pull them rather than remove with a punch.
Adios and good building