If you have time to prepare your lies then it just requires a sort of reframing. Do all your imagining ahead of time. Walk through and construct the lie. Fill

If you have time to prepare your lies then it just requires a sort of reframing. Do all your imagining ahead of time. Walk through and construct the lie. Fill in the details. You're not just imagining this one thing, you're imagining an entire alternate reality where this thing is true and all the implications that follow from that. When it comes time to answer questions the person is asking about the alternate reality you've imagined. No need to make things up - just recall back. I guess I'm saying the same thing as you, just in a different way - don't make something up on a moments notice, just have a different story that you tell.