Answer:
something with a volume of 64 ft³, such as a box 4 ft × 4 ft × 4 ft
Explanation:
The volume of the smaller box is (1 ft)³ = 1 ft³. So 64 of them require a box with a volume of 64 ft³.
The most compact of such boxes is one that is cube-shaped itself. Such a box would have dimensions of ...
∛(64 ft³) = 4 ft
A box that is 4 ft × 4 ft × 4 ft would hold the 64 smaller boxes.