I have never heard of parking slot. (AE)
Any BE speakers heard of this?

@Gerd101:
Meintest du vielleicht "parking lot" statt "... slot"?

Ersteres steht in Leo und bedeutet "Parkplatz"

I've come across "parking slot" plenty of times. Googling produces nearly 30,000 hits (+ 40,600 for the plural "parking slots") - but over a million for "parking spot" (+ 460,000) and 2.5 million for "parking space" (+ 3.5 million).

So take your pick!

And yes, they do all mean "Parklücke"

No, I did not mean parking lot. Perhaps slot expresses a tight spot, i.e. a spot with cars both left and right, so it's a challenge to squeeze in. A spot could be empty on both sides.

The picture of the slot of a slot machine might give an indication. It is lengthy in nature and you have to insert a coin into it aiming carefully...

Schau mal aus einem Hochhaus auf einen leeren Parkplatz. Was siehst Du?
Slots über slots.
Slots sind die Zwischenraeume zwischen den weissen Strichen, die da die Strassenbauverwaltung hat hinmalen lassen.
Diese Kästchen nennt man slot.

I would use 'parking slot' to refer to an assigned or reserved parking place. For example, doctors at a hospital are given a specific place to park.

I wouldn't say "parking slot." Here it's "parking spot" or "parking space." I suppose you could use "slot" for the spaces you pull into in a parking lot, where your car is parallel to the others, but not if you're parking next to a curb (and parking by a curb is, oddly enough, what we mean by "parallel parking").

Looking at the issue and talking into account the different points of view on the subject, to me, 'anon's suggestion makes best sense, as I can just envision "slot 01 allotted" to Big Boss

About "parallel parking": It makes sense, if you think of a car being parked "orderly", that is "near and parallel to the curb" as opposed to one parked skew-wiffed, i.e. in an angel to the curb or even in T-fashion...

Maybe you mean 'parking slut'?

or even 'parking slot slut'??

Parking slot exists, believe me. On airports we use this word to determine the time an aircraft can stand on position until it has to depart. It is similar to the departure slot, which describes the small time frame (15min)available for getting airborne. Aircrafts exceeding their parking slot are causing severe troubles to all the traffic coming after.