Here's the interesting thing. Even though I'm a stickler for usage, I never know the names of the tenses and how to explain why you say something one way and not the other.
I just know that a person can lie down, or you can lay a thing down. However, in the past tense, a person will have lay down, or laid a thing down.
I lie down to go to sleep, after which I have lay down to go to sleep. I lay the smack down on JrnymnNate, after which I have laid the smack down.
Also, a thing can lie flat, or you can lay it flat.
However, the slang use of "lay" is different. In that case, a "lay" is a noun, and the noun is verbed. "I need a lay." "I need to get laid." "I should have gotten laid just before my trip." "I'd better stop talking about getting laid."
It's like that.
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I am a delicate fucking flower.
https://beacons.ai/jesskent