Further on the edge vertex orientation. Here's a dome on a square foundation:
The shell to the right shows the interior space. A 3v hex-pent is essentailly 2.5v in roundness. The four half-equilateral triangles are not-necessarily-load-bearing, so two are modified to center an entrance on the porch.
The porch is shallow to be really usable -- increase it with a eave line connecting the front and rear to maintain a square plan.