In my first year of teaching English, I had to teach prepositions to sixth graders. I fumbled around for an entry point and reached out to a more seasoned colleague, who suggested that I employ the analogy of the rabbit and the log.
He said the approach was simple: draw a picture of a log and a rabbit on the board, and place the rabbit at different positions in relation to the log. This would draw out the use of prepositions. For example, "The rabbit is on the log." It sounded like a sensible approach.