Flesh Lips is a group of bosses fought together as part of the story.
They have very few attacks and will mostly slowly make their way above you, choking you if they get too close. The best way to fight them is with the shotgun. You can run around the room, making sure to stay out of their way and then position yourself semi close to one and shoot it. It only takes a few shots from the shotgun to kill one before moving on to the other. If you run out of ammo, you can switch to the pistol which can be shot from further away. Just make sure to occasionally re-auto aim so you dont miss. If you run out of ammo youll have to switch to melee. The pipe has a decent range but hitting them with it without taking damage requires precise timing. If you dont have the pipe, it will be very difficult not to trade damage and the battle will last a while. Hold down
to do a strong attack with it when they get close and immediately strafe whether you hit it or not. Regardless, defeating the first two will cause a third, slightly faster one who should also die fairly quickly. After all three die, the fight will end and the trophy will unlock.