renewable-resources/data/renewable/recipe/brain_coral_block.json

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "pattern": [
    "FF",
    "FF"
  ],
  "key": {
    "F": "minecraft:brain_coral_fan"
  },
  "result": {
    "id": "minecraft:brain_coral_block",
    "count": 1
  }
}