1-L-5: "The Clubshaft lies full length on a flat tilted plane." 1-L-6: "The Clubshaft always points at the Plane Line except when they are parallel to each other."
To fellow instructors who do not have the luxury of a plane board, torchlights or video to explain what being on plane per 1-L-5/6 means; set a clock at an angle just like your plane would be.
Simply explain that the second hand on the clock represents the clubshaft. If the student can keep the clubshaft on the flat tilted plane like the second hand on the clock face, he is then on plane.
If he can do that, then 1-L-6 will be simply a by-product.