Figuring out the airflow of the PS4 is like doing origami. The air comes in from the top of the back and goes out the bottom of the back. There is a aluminum-mobo-aluminum sandwich about a half inch thick in between.

The air come in through the top slots, over and through the bottom of the sandwich as the mobo is upside down. The air cools the sheet, cools the memory chips by little dimples on the sheet and then is sucked through the sandwich by many small holes in the sheet metal and then through the mobo- yes, there are airholes strategically placed on the the mobo! Look by the battery for most of them that are directly over the fan intake.

Now the air comes to the fan intake via those small holes and a couple of vents over the hard drive. The cutouts over the fan intake are particularly strange, square holes, small round holes, L shaped holes. From there it is out the fan across the top sheet, then the CPU/GPU heatsink, again with memory dimples, and out through the hot parts of the power supply.