You can make an inner cube with normals pointing inwards, and put a simple texture cube shader on it like this
( The power node is only because you couldn’t see the stars well ). And put another everyday cube around that with the glass/plastic material
You would need to make the outer cube material more carefully than that. The edges need that ‘intersecting plastic’ look, which is a bit like edge wear. But this is the basic concept.
You can make the edge wear procedurally, so I then copied this edge detection shader ( that only works for cubes )
to make the edge pop 
