Elevating the water does help keep it clean. Aim to have the level of the water/top edge of the tray at the level of the shortest chick's back. That way they can still reach in to drink.
I use an assortment of things to put under it. Overturned flower pot saucers, blocks of wood, bricks or any combination that gets it to the right height. If you have to choose between a little too high or a little too low, go lower.
I always have the brick or whatever it is resting on the actual floor of the brooder, with litter around it. That makes it much more stable. Having it resting on top of a thick layer of shavings makes it much more wobbly and easier to tip over.