Do they bring certified letters to the door, or do they just put a slip in your mailbox

Any item requiring a signature is attempted at the door unless there is unsafe access i.e. dog, locked gate. If no one answers, a left notice slip is left. The slip contains the address, and other pertinent information where the item can be picked up.

Generally, just a slip in your box unless the carrier knows the addressee is available, like the owner of a business during normal working hours. The slip will have the address for the post office where the certified item can be picked up, so make sure you go to that one specifically. You should also make sure you have valid photo ID when claiming certified items.