Spell "Create Pit", placing requirements?

[Falske]

Under the description of the spell "Create Pit" it says; You must create the pit on a horizontal surface of sufficient size.

Does this mean that there's a limit to how slanted a surface can be (i.e a low hill side) or can it only be cast on a surface so horizontal that you could, say, place a ball on it and the ball wouldn't move?

Also- what is 'sufficient size'? Can it be cast in a narrow alley or do you need a 10x10ft area +5ft adjacent (slanting area) all around the hole (so total 20x20ft area) in order to cast the spell?

cakethxbye

[boring7]

DM's call.

For slope, I would say 10 degrees or less, and consider it pretty generous.

For area, I would say "20x20".