"leave it on the porch" isn't even a thing in the UK, unless you specifically nominate it as your acceptable secure place.

Amazon knock on the door, if you're not in then they'll come back tomorrow, and if you're not in, then they'll try the next day. If you're not in three days in a row they'll hold the package for three days, to give you time to arrange one final delivery attempt to your home, Amazon locker or pick-up point (neighbourhood shop). Eventually they'll just take the package back and refund you automatically.