here is a lovely diminutive complete Soma cube (everyone should have one) in a box that is far too large for the completed cube (it is 4x4x4 to the Soma's 3x3x3) – the pieces just seemed to fill the bottom half in a haphazard manner. The explanation was that this is an 'anti-slide puzzle' which is something I've only ever attempted maybe once in my puzzling history. The aim is to place all the pieces in the box so that the entry to the box (4×4) is filled and held up by a pile of the other pieces. However this isn't the entire story… the solution is only complete when the construction that you have made is completely stable and will not slide at all.

Once you have created your potential solution then shake the box vigorously in all directions to see if any pieces can move.