Clearly, Nephi did not receive just one revelation at the beginning on how to build the ship. He went many times into the mountain to pray, and the Lord showed him many things, more things than just about the ship. The mountain was a place of revelation and inspiration. Nephi was a man who believed in prayer. At the end of his narrative he will affirm: "But behold, I say unto you that ye must pray always, and not faint; that ye must not perform any thing unto the Lord save in the first place ye shall pray unto the Father in the name of Christ, that he will consecrate thy performance unto thee, that thy performance may be for the welfare of thy soul&" (2 Nephi 32:9). He learned that lesson at the beginning and never forgot, as it was reinforced through his experiences that he must pray always and over everything.
He said in 2 Nephi 4:25: "And upon the wings of his Spirit hath my body been carried away upon exceedingly high mountains. And mine eyes have beheld great things, yea, even too great for man; therefore, I was bidden that I should not write them." We do not have all of the great and marvelous things that Nephi beheld when he was on the mountain and carried away by the Spirit, but we know that these revelations were facilitated through Nephi’s diligent prayers.
Book of Mormon Central, "Why Must One Pray Always to Endure to the End? (2 Nephi 32:8–9)," KnoWhy 298 (April 10, 2017).