Place the used capsule foil-side down on the lid of the box.
Use the masher to mash the capsule, breaking the foil and dumping the grounds in to the box.
Tap, crunch, poke or use the knock of the masher to knock all of the remaining grounds in to the box.
Recycle the Aluminum capsule, compost the coffee.
(optional: rinse the crushed capsules to get ALL the grounds out.)
Mashing capsules can be therapeutic...