Nephi states that the Lord showed him "from time to time" how to work the timbers:
Similarly, we are asked to shape our lives after the manner the Lord has shown us, not after the manner of men.2 Now I, Nephi, did not work the timbers after the manner which was learned by men, neither did I build the ship after the manner of men; but I did build it after the manner which the Lord had shown unto me; wherefore, it was not after the manner of men.
How are we to know how to shape our lives. Here's verse 3:
Nephi's brothers do not have the same trust in God, and so although they help, the process probably seems much more unusual and arbitrary to them.3 And I, Nephi, did go into the mount oft, and I did pray oft unto the Lord; wherefore the Lord showed unto me great things.
Perhaps it is the same with the commandments--if we regularly receive direct inspiration from God as we "go to the mount oft" and "pray oft", we will have a much easier time following the Lord's instructions than if we act out of a sense of obedience alone or based on cultural of familial expectations.