I've drilled hooks into the joists in the ceiling, and I hang a panel from there above the spot where I record, then I stand the other panels in the corner away from the wall, and sort of build a booth inside the room. Sorry I can't take a picture, as I'm not there right now.
The problem with putting absorbent acoustic treatment directly on the walls is that it will only absorb effectively at wavelengths that are longer than four times the thickness of the panel.
For example, if your panels are 15cm thick, like mine, and you put them on the walls, they will start to become ineffective at wavelengths longer than 60cm, which is 566 Hz.
With poor sound absorption below 566Hz, and near total absorption above, you end up with a boomy/boxy sounding room.
However, if you're only going to record sources that are higher pitched than 566, it won't matter.