When TTC is best to stay lay down after sex?

Sam • 🇬🇧 UK Full Time Mum, 2YO girl, pregnant with 2nd
Just wondering if most people stay lay down after BD when trying to conceive. I have read that it's best not get up for 15 minutes afterwards and also read that it doesn't make any different of you do or not as sperm reaches your cervical canal in seconds.
I've been laying with my legs in the air after BD during my fertile week but I get bored after like 5 minutes lol
Does it really matter?