Calculated vertexes in a spreadsheet. Created a module extending polyhedron to approximate saddle surfaces.

Print one copy of the pieces (parhex.stl).  All 16 pieces are printed as they would be located in the box.  

An effective variation is to print two copies of the pieces (parhex_p) in contrasting colors, and select for a checkerboard pattern, and print one copy of the box (parhex_n).