This is the version to hand to a teacher or a parent rather than a maker. No function generator, no bench amplifier — the plate is driven from a speaker and a phone tone generator, with the salt or sand doing the rest. The video runs at 100 seconds and shows the assembly and several frequencies without narration padding.
The channel's description lists what it is meant to teach: sound waves, frequency in hertz, resonance, nodes and energy transfer. There is a longer written article on their site with a lesson plan, which is the part that makes this more than another short clip. The build itself is unremarkable, which is the point — it lowers the barrier to a first plate to about an afternoon and pocket money.
Worth watching alongside a more serious rig video to see what you actually gain by spending money on a proper mechanical driver.