Giving a single moment of thought to what happens when the paste is squished to this should lead everyone to the conclusion that a square that is equidistant from the edge to the center is the right pattern with maybe a dot it the middle for piece of mind.
Youtube recommended a similar video where they tested various patterns. Spreading paste over the the whole heat spreader resulted in a small air pocket, while the same method with an additional paste dot in the middle didn't have such issues. But at that point maybe you're getting too much paste instead, as mentioned you want as thin layer as possible. At the end of the day, it probably doesn't matter much anyway.
That wasn't tested there.