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Json files (datapacks) is the way you do this. You will find a lot of information about them on the internet. The main community developed documentation I know about are: https://misode.github.io/ and https://minecraft.fandom.com/wiki/Data_pack the second of those is really just a collation of all the minecraft release notes. The first also has the vanilla world gen files: https://github.com/misode/mcmeta/tree/data/data/minecraft/dimension https://github.com/misode/mcmeta/tree/data/data/minecraft/dimension_type https://github.com/misode/mcmeta/tree/data/data/minecraft/worldgen Those json files are just configuration files that create java objects using codecs: https://forge.gemwire.uk/wiki/Codecs either as; * simple values or "records"/collections of them * references to objects created from other json fles * references to objects that are constructed and registered programmatically such as the vanilla provided presets, dimensions, chunk generators, carvers, features, structures, etc. If you want to create flat terrain, I would suggest you start with vanilla's FlatLevelSource and FlatLevelGeneratorPresets and follow the rabbit hole. As for tutorials, even if you find one, it is likely out-of-date. The modern worldgen has been marked as experimental since 1.16. Mojang keep iterating on it without any real constraints of compatiblity across versions - the json file formats are more stable than the code they configure I would suggest you read the vanilla source - net.minecraft.world.level.levelgen.* and net.minecraft.data.worldgen.* or search on github for up-to-date implementations by other mods of the classes you are interested in.