Okay... then what would this closed, finite-sized universe be floating in? A petri dish sitting under somebody's microscope?
My vote is that it is spherical with infinite space in all directions.
The idea is that the volume is finite, yet unbounded. There is no way to picture this. But, we can picture a finite two dimensional object, that is unbounded.
If the area of the earth is finite, then what happens when you get to the edge?