Players want to cast Temple of the Gods on a small floating square at sea. (It involves the shape water cantrip, but I want to put that aside for this question). The spell says it requires to be cast on ground-- so right there is a solid argument against allowing this, but I can see the argument for the floating area to be considered "ground" as long as it's afloat. The issue I want clarification on is size of the area, though. Spell says it requires a 120ft cubic space. That, coupled with the "ground" requirement, leads me to believe that a 120 ft square of "ground" is required. However, the ambiguous wording requires a logical leap.
Disregarding "rule of cool," or the fact that we're really stretching shape water-- does the area of the ground matter when casting Temple of the Gods?