She lay on the bed, her arms and legs splayed out.

她四肢摊开躺在床上。

《牛津词典》

She lay on the bed, her eyes closed and her bosom palpitating.

她躺在床上，双目合拢，胸部颤抖。

《柯林斯英汉双解大词典》

The girl lay on the bed asleep.

女孩躺在床上睡着了。

youdao

So you would say in the past tense "I lay on the bed because I was tired."

VOA: special.2010.02.11

His head began to ache, and Mister Mindon lay down on the bed.

VOA: special.2010.05.29

His head began to ache, and Mr. Mindon lay down on the bed.

VOA: special.2009.01.31

He said Gilliard had got the statue from the garden and the knife from the kitchen before going upstairs to attack his wife in the bedroom as she lay on the bed.

BBC: Frederick Gilliard jailed for killing wife with statue

It was only when I got home at midnight and lay on the bed with my sleeping five-year-old daughter that the tension of the day gave way to fear of what was to come.

BBC: Remembering the Pentagon attack

She lay down on the bed, her feelings concentrated at the forefront of her mind like an immensely weighted black point, incomprehensible.

NEWYORKER: In Other Rooms, Other Wonders