Where is the air inlet on a Mac mini (2018) for the cooling fan? On the Mac mini (2018), where is the air inlet for cooling the innards of this computer? 

I have looked at the iFixit teardown. It shows the fan blowing out the broad outlet across the back of the Mac mini, below the USB-C ports. I certainly can feel the warm air exiting this outlet. 

➥ Where does the air enter the Mac mini? 

The bottom is either solid metal or covered by the non-slip rubber. I see no other inlets on the backside. So I am left puzzled.

I am concerned about not blocking the air inlet, to maximize cooling efficiency.
The air inlet on the Mac Mini (2018) is located on the bottom. If you look closely at the circular plastic disc, you'll see that there's a gap between that and the metal part of the computer. This is the air inlet!

The electromagnetic shielding beneath the plastic disc is perforated, allowing air to move. As shown on iFixit: