He takes a knee next to her, as though about to recite some romantic poetry, and casts a Silent Image to produce some three-dimensional visualizations of spellforms in front of her.
"Have you cast a cantrip yourself? They are designed to be caught and reset, but that is something that the caster learns to perform reflexively, they do not flow back into their original form by themselves as much as it might appear so to an outside observer."
"As you might be aware, we prepare our spellforms with a mnemonic matrix, like the headmaster's memory palace. Through rigorous exercises of the mind we learn to exert a very weak grasp on the material and mental essences. That grasp is too feeble to produce any noticeable effects, lesser than even Prestidigitation, but with diligent effort we can use it to build up knots of tension that when released do accomplish something more significant. Every complete loop increases the power and complexity of the spell's effects, and it needs to be a complete loop or else the spell won't stabilize. That's why there are no spells of two-and-a-half circles."
"But the most basic spells at all are those weak enough that they don't even need a single loop. These zero-circle spells, or cantrips, rely on that weak grasp alone to supply the force. You maintain the tension just by holding them ready to cast, and when you release them they can be caught again once the effect has been produced and before they fully disperse, squeezing them back into shape."
That will be accompanied by a visible version of the spellforms being assembled and released, the cantrip one then returning to its original form with a disconcertingly realistic human hand pushing one of the bends back into place to illustrate how it is 'caught'.