It then looks as if it moves with the player.

Ok I had the choice of doing 2 things. Bot resulting into 2 problems:

• 1: Enable the Depth buffer. Fixing the exact issue what you are having. (The box isn't moving its just a optical illusion because no depth) But that would mean you don't actually know how the big the box is without digging all blocks around it. (Underground that is painful)
• 2: Disable the depth buffer. This causes the issue you are having. But it allows to see how large the box is. Yes there is optical illusions included but the general idea for things is provided. And there is no surprises that you couldn't see.

I went with Option 2 and that will not be changed.