In "Cubism Revisited" in the August 1978 Word Ways I presented a non-symmetrical word cube of the sixth order. This cube, although structurally perfect, contains a small number of non-words. I recently had another go at this problem -- here is the result.
"More Word Cubes,"
Word Ways: Vol. 12
, Article 3.
Available at: http://digitalcommons.butler.edu/wordways/vol12/iss2/3