The Testimony of Eight Witnesses, printed at the front of each Book of Mormon, says:
Be it known unto all nations, kindreds, tongues, and people, unto whom this work shall come: That Joseph Smith, Jun., the translator of this work, has shown unto us the plates of which hath been spoken, which have the appearance of gold; and as many of the leaves as the said Smith has translated we did handle with our hands; and we also saw the engravings thereon, all of which has the appearance of ancient work, and of curious workmanship. And this we bear record with words of soberness, that the said Smith has shown unto us, for we have seen and hefted, and know of a surety that the said Smith has got the plates of which we have spoken. And we give our names unto the world, to witness unto the world that which we have seen. And we lie not, God bearing witness of it.– The Testimony of Eight Witnesses
If Joseph had created the plates himself we would not have expected the witnesses to be convinced they were genuine having handled them. Why think that Joseph was not only a creative mind who could write the Book of Mormon but also a master craftsman?
The testimony of the eight witnesses, who handled the plates, is compelling evidence to the truthfulness of the Book of Mormon.