You can simply make the box move at the same time as the player by pinning it to him while he touches it while holding the interaction button.
not sure exactly without any concept of the circumstances
But whit this method, if you push the box to a 'cliff', it still pinned on the player..
And that's why I think the best thing to do is put a platform and a solid behavior to the box... but, as the player have a platform behavior, it treat the box as a wall... so, the movement is 'flicker'.