Is it allowable to cast a "Wall of Ice" spell in its hemispherical configuration in mid-air, or upside-down? The description of the spell is very explicit about it being anchored when it's in the flat configuration, but does not mention anchoring or direction for the hemisphere configuration.
The spell text says "This spell creates an anchored plane of ice or a hemisphere of ice". That means that the plane has to be anchored, but the hemisphere doesn't. If it had meant that both have to be anchored, it would read "This spell creates an anchored plane or hemisphere of ice." Also note that the word "anchored" appears three times in the plan section and not at all in the hemisphere. Looks to me like the authors were very careful to limit the anchor verbiage solely to the plane.
To me, that means that, yes, you could create that thing in mid-air or upside-down.