Jeremy Galvagni showed that every integer k has at least one solution. In particular, a 1×k2 rectangle can be surrounded by k2 non-touching copies of a 1×k rectangle.
Joe DeVincentis showed that the only numerical configurations where area 6 is the largest area are the ones shown below:
And then he proved that all such solutions for the k=2 case are just scaled up versions of one of the solutions above. Thus only area sets that are multiples of {1}, {1,2}, {1,2,3}, {1,2,3,4}, and {1,2,3,4,5,6} are possible!