Stoneblock
To create a Stoneblock-like modpack, you can simply set the surface settings as shown in the configuration below.
config/skyblockbuilder/common-config.json5
{
  "World": {
    "surface": true,
    "surfaceSettings": {
      "minecraft:overworld": "minecraft:bedrock,382*minecraft:stone,minecraft:bedrock",
      "minecraft:the_nether": "",
      "minecraft:the_end": ""
    }
  }
}
The downloaded file also sets the default world type to Skyblock, generating Bedrock at the top and bottom of the
dimension. There is only one spawn point, and a starting inventory is included, as shown below:
config/skyblockbuilder/starter_item.json
{
  "items": [
    {
      "item": "minecraft:wooden_pickaxe",
      "nbt": "{Damage:0,Enchantments:[{id:\"minecraft:efficiency\",lvl:2}],Unbreakable:1b,display:{Name:'{\"text\":\"Infinite Pickaxe\"}'}}"
    }
  ]
}