Adjacent Placement of Objects according to varying height

Hello,

I need to place a stack of boxes on top of each other based on the height of the previous box.

The boxes vary in height.

 foreach( cBox box in currentLevel.mMiddleRack.BoxWeightList)
             {
                 box.mBoxImage = (GameObject) Instantiate(boxTemplate);
                 box.setBoxPosition(firstBoxPostion.x, firstBoxPostion.y, firstBoxPostion.z);
                 firstBoxPostion.y += box.mBoxImage.transform.localScale.y;
                 firstBoxPostion.z -= 1.0f;
 
                 box.shapeBox();
             }

The Result:

Please Guide me!

Thanks