First, clean the engine. Try to cover up electrical connectors and the alternator, remove the battery. This is a good time to clean the whole engine bay. Spray with degreaser and soapy water. It will make finding the leak 1000 times easier.
The problem is that once there's a leak, air blows the oil all around. So sometimes oil moves down, sometimes it moves towards the back of the car.
Try looking at the back of the valve cover and the EGR weep hole.