Having your arm slung over a little bit makes it look like you're casually sitting there and not really posing for a picture so much.

稍微搭一下手臂，看起来就像你随意地坐在那里，而不是摆拍。

The previous morning I had woken with his big arm slung over me and something hard pressing into the small of my back.

前一天早上我醒来时，他的大胳膊搭在我身上，有什么坚硬的东西压在我的后背上。