Adding a Custom Dimension to Flat Bedrock with a JSON File

The mod ships with configs for the Overworld and the Nether, but any dimension that has a bedrock layer can be added by hand. This is useful for modded dimensions that generate their own bedrock floor or ceiling.

Create the JSON file

Go to /config/flatbedrock/dimensions/. You will see the existing dimension files there. Create a new file with a .json extension and a name you will recognize, for example the name of the dimension you want to affect. Copy the structure of an existing file so you keep the same keys: dimID, genTop, genBottom, retroGenTop, retroGenBottom, and fillBlock.

Find the right dimension ID

The dimID field is the numeric identifier of the dimension. The Overworld uses a low positive number and the Nether uses another fixed value, so check the file that already exists for the dimension you are copying from. For a modded dimension, look up its registered ID rather than guessing, because an incorrect number will silently apply your settings to the wrong place.

Set the switches

Set genTop to true only if the dimension has a bedrock ceiling you want flattened. Set genBottom to true for a bedrock floor. Use the retroGen versions if you want existing chunks changed as well. Finally, set fillBlock to the block you want left behind, using the full namespaced block name.

Test carefully

Load a fresh test world first. If the layer does not change, recheck the dimension ID and the spelling of the block name.