How to project a 2d sprite onto a 3d object?

For exemple, on the image below, the red square is under the 3d object and I would need it to be projected over it instead. I tried putting the square in a new layer above the one that contains the 3d object but it didn't worked. Also the only way I found to make the 3d object appear under the sprite is to put an higher Z value than the hight of the 3d object which is not practicle. So I would like to know if there's a way to achieve this?

Put the red square at a higher z elevation than the 3d object. You can find the Z Elevation in the Properties sidebar menu for the red square.

But this completely changes its position, I need something that can put the sprite over the 3d the same way layers or Z order would do.

Put the red square on a new layer and change the layer rendering mode to be 2D. Now if you put the layer above the 3d box layer, the red square will appear above the 3d box without changing the z elevation