Top left. Also, pro tip: if you're a dork like me who sticks their hands in their pockets and accidentally unlocks their phone with the fingerprint scanner, remove your non-dominant hand's fingerprints and always put your phone in that same hand's pocket. E.g. if you are right handed, remove your left hand fingerprints and always put your phone in your left pocket. That way you need to remove the phone from the pocket and transfer it to your other hand before you can unlock it.