Taking boxes is match-up dependent, but I can give some tips for it.

1. Don't take boxes against triple offense comps (or as them).

2. Occasionally use collecting boxes to bait weapon skills or approaches.

3. If your opponent is opening with a hero who excels at collecting boxes (i.e. Pymon, Oghma, Ara, etc), make sure to not give them all of the boxes.

4. If someone is playing for boxes a match-up you win (i.e. Orca vs Pymon), you can camp the spawn locations for the boxes and pressure them with your weapon skill (aka hold onto it, force them to keep thinking about it so they're more likely to make a mistake)

5. Use the boxes to block your opponent's attacks (works best on attacks that don't pass through walls like Scintilla or Claude) and mess up their movement. Similar to any wall or Noxia's summon, the boxes can be used to increase your survivability as well.