So far all the resources i've look at are outdated 

What is this biome being created for? A custom dimension or a vanilla one (e.g. overworld, nether, end).

Overworld

 

The process requires a bit more work then. All worldgen stuff is handled through jsons now. You could probably find how they need to be formatted on the mc wiki. So, just format them according to that. You can also look at slicedlime's vanilla world gen extraction for examples. As for getting it in the overworld. You need to do a few things. Existing dimensions use entries hardcoded to be in code instead of through json making them inaccessible from pure json. To get around this, you have to supply a dummy entry and handle it that way.  So, register the biome using any forge registry process and supply some dummy biome to the instance. It will be replaced by the json when the server is loaded. Finally, you will need to call BiomeManager#addAdditionalOverworldBiomes within the synchronous work queue of FMLCommonSetupEvent. This adds your biome to the overworld biomes. Note, that this takes a registry key which can be gotten using RegistryKey#get and supplying Registry#BIOME_REGISTRY as the first parameter and the resource location of your biome as the second.

 

In summary:

1. Create biome json.

2. Registry dummy biome to forge registry.

3. Add biome to overworld biomes within common setup.

 

Any other information can be derived from the primer.