Nope you can leave a note thats just fine. I did it with mine and they had no issues. When you check the tracking it'll say indirect signature required. Meaning a neighbor could sign for it or whomever is home when they arrive, or you can leave a note signed and they'll leave it wherever you want them to.
As everyone says, they require an "indirect signature" so leaving a note with your tracking # and signature, saying please leave at front door, or something similar, should be enough. Otherwise, they will leave you the doortag and you can pick it up at their sorting location the same day (Mines said any time after 6 pm). I did the latter as I didn't feel comfortable with them leaving my phone at my door steps when I wouldn't be home for atleast another 5 hours (they came by at 11am)