In Alma 17 we read of when Alma is reunited with the sons of Mosiah. The next 10 chapters of the Book of Mormon are a flashback to what had happened to each of them (Alma 17:5 to 27:15).
What is particularly impressive is that Alma 20:30 to Alma 21:14 is actually a flashback within the flashback. Alma 20:28-30 tells the story of Ammon rescuing Aaron and others from the land of Middoni. Then Aaron’s record of his own preaching, imprisonment, and rescue is laid out in Alma 21:1–17.
How did Joseph Smith manage to dictate this part without getting confused? Why didn’t the scribes mention him tripping up at this point?
This example shows the complexity of the Book of Mormon and acts as another piece of evidence that Joseph did not write it himself.