To make a chocolate bowl, use a bowl from your cupboard and cover the outside with plastic wrap. A bowl with a smaller bottom that the opening at the top and coat the outside with melted chocolate (do this a couple of times to get the correct thickness you want) You could make a pattern in the chocolate by dragging a fork over the last layey, before it completley sets. Ease the real bowl out from the inside
If you want a box,you could make one from cardboard, cover the same way then remove the cardboard by tearing it from th inside.