Every set in our window starts with three pieces of different heights (sample note).
Put the tallest piece at one end, a hand’s width from the edge. Add a piece about half its height towards the other end, then finish with something low and wide. Look from across the room: the line through the tops should fall from one piece to the next.
If it still looks lined up, move the middle piece forward a few centimetres. Depth matters as much as height.