For the best discussion, in detail, of embedded readings, see this discussion on Laurie Clarq’s website.
Since Latin teachers often have stories in their textbooks which introduce vocabulary too quickly while sheltering the grammar (the exact opposite of what works), this top-down approach to embedded readings is perfect. You can do this with a story from your textbook or one from Vergil. Doesn’t matter. Same process. You are creating a version of the story in which you shelter the vocabulary, removing unnecessary vocab and replacing some with synonyms that you know that they know. Some readings require several embedded versions to bring them from where they are to where the reading is and some only require one. Creating embedded readings makes it so clear why students cannot be expected to READ classical authors after only 2-4 years. It’s a POWERFUL form of CI, though, and students love this doorway into reading.