How can I go about creating another world generator in PMMP but the world being flat but with still small hills and small ponds(not lakes) and trees of course.
I have no clue about the code to generate it like you said, but you can begin by creating a class that extends pocketmine\level\generator\Generator. You may want to look at MyPlot for an example. You could probably look into PMMP's default generator for everything else.