He showed me how to drape the sling over my left shoulder and across the chest so that the pouch lay easily accessible to my right hand, allowing the best in journalism, fiction, and cartoons to be swiftly extracted and sold to a citizenry whose happiness and security depended up on us soldiers of the free press.
参考译文：他给我示范怎么把包的背带斜挎在左肩上，这样袋子正好挂在右手所及之处，于是我就能很快地把最好的报道、小说和漫画抽出来卖给市民们，我们这些自由新闻界的尖兵掌握着他们的幸福和安全。

你的理解是正确的，lie是处于..状态

lie 处于…状态,后面接形容词或过去分词，用来说明“主语所处..状态”

She turned back to the Bible lying open in her lap. 

她将注意力又转回到摊放在腿上的《圣经》。

The picture lay hidden in the archives for over 40 years. 

这张照片在档案室中藏了40多年。

I have lain awake all night, thinking of this.
我想着这事,一夜没睡着。

The farmland lay barren.
农田成了不毛之地。

The machinery was lying idle because of the strike.
机器因罢工而闲置着。