Prayerfully study the following scriptures and other materials:
This lesson could occupy at least two weeks of class time, if not an entire semester. There were many divine interventions during the time period that the lesson doesn't discuss. I have an entire book on these events: Whatever Happened to the Golden Plates? It's impossible to summarize it in this post, but here are some key points for teachers to consider.
D&C 10. Everyone focuses on the part of D&C 10 that discusses the lost 116 pages. However, D&C 10, is also partly an answer to D&C 9:2, which promises Oliver Cowdery that the Lord has "other records" that Oliver would "assist to translate." What other records was the Lord referring to? The traditional explanation suggests the Book of Moses or the Book of Abraham, but neither of these were records that Joseph translated. They were both the product of direct revelation. So either D&C 9:2 was never fulfilled, or else it was fulfilled in the very next revelation: D&C 10.
D&C 10 refers to the "plates of Nephi" several times. IMO, that's because Joseph and Oliver did not have the plates of Nephi yet. These plates were not part of the record Moroni put in the box. They got them later. That's why they had to go to Fayette, where they translated 1 Nephi through Words of Mormon.
You can see this in the Title Page, which Joseph said was on the last leaf of the "original Book of Mormon." The Title Page refers only to abridgments, not to any original plates. The "plates of Nephi" were not abridgments. That tells you they were not part of the "original Book of Mormon" that Moroni assembled and put in the box.
The traditional interpretation of Words of Mormon doesn't make sense, either. If Mormon attached the small plates of Nephi to the record, Joseph would have translated them before he got to Moroni's later additions, but he didn't. The explanation that the Lord knew in advance that Martin Harris would lose the 116 pages presents all kinds of philosophical issues we don't get into during class (such as, was Harris predestined to sin?).
It makes more sense that the Lord made provisions in advance for whatever might happen as a result of human choices. If Harris had not chosen to take the pages, or he had not lost them, or if Joseph had accepted the Lord's first answer to the request, we never would have needed the small plates.
What if a different part of the translation had been lost or destroyed? I think the Lord had alternative backups prepared for any eventuality.
Where did Joseph get the plates of Nephi? You can probably figure it out, but I'll post more about that later.
A word of caution. There's a recent trend claiming that Joseph didn't use the plates to translate. (Actually, it's an old anti-Mormon claim, but it's been revived recently by books I won't name, but they're published by Deseret Book.) Under this theory, Joseph only read the words off the seer stone, which he put in a hat, which he then put over his face. D&C 10 repudiates that claim. If Joseph merely read the words off the seer stone, why would the Lord need to tell him to translate the plates of Nephi? It makes no sense. He would have just kept reading whatever words the stone gave him until he was finished. Going back to the Book of Lehi wouldn't have been an issue in the first place.
Unless the stone was making a mistake, which opens another huge can of worms.
Furthermore, what difference would it make to have a portion of the plates sealed if Joseph never used them anyway, and couldn't read the characters if he did?
The historical record does show that Joseph used a hat to read the words on the stone (and/or the Nephite interpreters). However, the record also shows him interacting with the plates. I think the best interpretation of these accounts is that Joseph did consult the plates. He copied the characters and learned to translate them. But he needed the seer stone to put into words the thoughts he had as he interpreted the characters. That's the part that Oliver Cowdery didn't understand; like many people today, he thought Joseph just read the words off the stone.
Obviously there's a lot more to the translation story, but I just hope teachers don't perpetuate the recent fad that Joseph did nothing but read the words off the stone in the hat.