Green’s Dictionary of Slang

box n.2

[fig. use of farming jargon box, to mix up two herds or flocks by mistake; note also earlier in a box under box n.1 ]

(Aus./US) a blunder, a mix-up, a mess; a predicament.

implied in make a box of below.
[Aus]Baker Popular Dict. Aus. Sl. (2nd edn).
[UK]A.E. Farrell Vengeance 29: There was a bit of a box on with another X bar E Hereford that seemed to have an infected shoulder.

In phrases

make a box of (v.)

(Aus.) to make a mess of.

Australian Star (Sydney) 5 Sept. 5/1: —Mr. Webster gave evidence also from memory? —Yes. And he made a box of it? —It seemed so from the papers. What he said at the Police Court was the opposite to what he told the Commission? —I believe so.
[Aus]Baker Popular Dict. Aus. Sl.
[Aus]Baker Aus. Lang. 65: To confuse or muddle something is to make a box of it.
[NZ]McGill Dict. of Kiwi Sl. 71/2: make a box of make a mess of.
[NZ]McGill Reed Dict. of N.Z. Sl. [as cit. 1988].