I agree that a single flat piece of terrain would be boring.
What could be done is instead of having a real hill, have a platform that represents a hill instead. I think you could get away with that cartoony level design.
Viewing post in Cucumber Chaos jam comments
Hmmm...I think what you want, in this case, is to have cucumbers ignore platforms and all go to the floor, but introduce BIG BOI CUCUMBER that not only reaches the height of the platform, but lands hard on the ground, causing the other cucumbers to "Jump" to at least platform height.
Oh yeah, you wanted to know how to make them ignore platforms. Take a look at "Collision Masks/Layers"