Jeff,
I had a beginning student show up, we're talking a minimally practicing 6th grader. No book, no guitar pick, no handwritten lesson, in other words completely unprepared. He's on the fourth string in the method book so he knows a little bit about reading.
So I broke out some manuscript paper and told him under the circumstances we can't worry much about playing but we're going to study.
I told him what a C major triad was, what it looked like on the staff and how it fit on the first two guitar strings. I said this is a given, they all look like this up the neck on these two strings, find an F major triad. Of course he didn't learn that root note so high on the neck yet, but he does know B to C and E to F are half steps so we walked up that second string one letter name at a time. Using that he found F major triad, and consequently A and C notes on the first string. G required a bit of thought but he got it and again two new notes, B and D. He knew and understood this and I had him play them a few minutes.
Next I told him we can change the order of the notes and explained first inversion. We did this for C, wrote it out, then played both inversions and saw how these stacked and looked on the staff. Did it with the other two G and F.
I left the second inversion for him to figure out, with the help of telling him which string had two notes.
The idea here was learning a major triad its formula, all the notes in the key of C on the first two strings without really trying to do that, and never come unprepared. Truth is he was pretty engaged in the whole thing. I don't know if he'll do that work, but he understood. I've never covered that bit of theory for so new a student.
I was trying to save a trainwrecked lesson, and hoped I did the right thing.