What version of the mod, Forge/Neoforge and Minecraft are you using?
Forge 43.3.2

Describe the bug
The game freezes and generates a crash report when creating a superflat world.

To Reproduce
Steps to reproduce the behavior:

1. Launch game
2. Go to world creation menu
3. Create superflat world
4. Game freezes

Expected behavior
Of course, expected behavior is to load into the superflat world without issue.

Screenshots
If applicable, add screenshots to help explain your problem.

Crash report (if necessary and/or applicable)
ex: [upload file here]

Log file (should be titled latest.log, if applicable)
ex:
crash-2023-11-28_01.53.53-server.txt

Additional context
This seems to be a conflict with another mod. Not sure which one though.

Looking at your crash log, it appears you’re using an older version, v1.2.
This bug was actully already reported in issue #22 (affected all non-default world types) and then fixed in v1.3, so I’d recommend updating to the latest version of the mod (currently v1.3.3 as of writing this comment).

If updating doesn’t fix it then you can reopen the issue, but since I’m about 99% sure that’s the problem, I’ll close the issue for now.