Stoneblock
To create a Stoneblock-like modpack, you can simply set the surface settings as shown in the configuration below.
config/skyblockbuilder/world.json5
{
  "surface": true,
  "surfaceSettings": {
    "minecraft:overworld": "minecraft:bedrock,382*minecraft:stone,minecraft:bedrock"
  }
}
The downloaded file generates 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_inventory.json5
{
  "items": [
    {
      "Slot": "mainhand",
      "Item": {
        "id": "minecraft:wooden_pickaxe",
        "count": 1,
        "components": {
          "minecraft:enchantments": {
            "levels": {
              "minecraft:efficiency": 2
            }
          },
          "minecraft:unbreakable": {},
          "minecraft:custom_name": "\"Infinite Pickaxe\""
        }
      }
    }
  ]
}