Yuk! spoon... I'm way to claustaphobic for that...
Me, stomach, unless I'm on the floor, then back, but on the couch, I'm definitely side, same with the chaise.
And when I slept on the hood of my HMMV, I was side there too...
And in the car on the way to work, I'm sitting...chin on chest, but that's not an option here...
...So, it really depends on the location.
But spooning is never an option.