Get hold of a keyboard, even a toy will do, if all the notes work.

Show the learner a scale, then show how most chords are produced by hitting every-other note in the scale.

Then show a few inversions.

Then show how to play scales on the guitar. There are two ways: by going up a string and skipping certain frets or by finding the scales in blocks, using different strings. The fingering is different from a keyboard, but the idea is the same - chords are basically every other note in the scale you wish to play.