I often have a spectator hold a small tray what serves as a table for the box and extra coins.

No one has ever tried to pick it up and examine it, but the idea that they could seems to satisfy the audience.

You can also have a spectator remove the box from a sack and hand it to you. Since they have no idea of its purpose "it is just a box."

^ funsway, I like your approach.

I do not have an issue with handing out the box boston or other. The issue is handing out the lid and box to the same person. Yes the recess in the bottom is use to conceal. But the critical thing with the box is the fact that the box looks the same with the lid on the top or the bottom.