This mod does one thing...Makes the bedrock layer flat, and nicer. The mod adds a block that replaces bedrock with a configurable texture(still unbreakable like bedrock).
Simple drop the mod into the mods folder and enjoy flat bedrock layers. You can also edit the config to change the texture of the new bedrock block.
3.0.2 and higher lets you add dimensions other than vanilla for flat generation.
If you add this to an existing world, then only new chunks will have flat bedrock. (Retro generation coming soon.)
Suggestions? Bugs? Open a ticket.