Green’s Dictionary of Slang

(Aus./N.Z.) to make a blunder, to mix something up; spec. of cards, to shuffle.

1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 26: BOX, BOXED: in common use to mix or mixed. ‘Box the cards’ is a domino phrase. House-painters speak of boxing mixing two lots of paint.
1950		A. Buckeridge Jennings Goes To School 123: You haven’t half boxed it all up nicely [...] I wouldn’t be in your shoes when we get back.
1996		(ref. to 1963) D. Healy Bend for Home 192: She can box the cards like a pro.
2003		McGill Reed Dict. of N.Z. Sl.