any ideas for how to keep level, a windowbox on a sloped sill?
I have an exterior cement windowsill that overlooks my balcony. I want to sit a windowbox on the sill, but I want the windowbox to be level so that when I water the plant, it gets watered evenly and drains evenly and so that it simply looks more attractive also (it doesn't look so nice sloping downward). I was thinking of putting a sloped piece of wood underneath, but then of course there's the issue of the wood getting wet. A few rubber doorstoppers might also work placed beneath the box but then...that wouldn't look so attractive.
I cuold also put some rocks but then any time I need to pick up the windowbox I'd probably have to spend some time adjusting the rocks again so that the box securely rests on top of them...