Ideally, store one item per box, fitting the box to the dimensions of the piece, if you can afford the room and the materials. Barring that, there are some alternatives. Museums dissatisfied with commercially available box sizes or materials have trained volunteers to make boxes that match the item to be stored. In-house boxes work well for gowns or fragile objects. Some volunteers become experts at box designs that solve complicated storage problems.
Boxes can incorporate fold down sides and sliding bottom trays to improve artifact removal.
Learning to make boxes is an important collections care skill. The Northern States Conservation Center provides box-making courses to museums for staff and volunteer training. A list of our courses is available here . Instead of stacking items directly on top of each other within a box, convert box interiors into multiple layer storage units. Some companies sell acid-free cardboard trays and dividers for their box interiors.