pumpkin-java-multiversion/assets/datapacks/26_3/data/minecraft/recipe/magma_block.json

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "key": {
    "#": "minecraft:magma_cream"
  },
  "pattern": [
    "##",
    "##"
  ],
  "result": {
    "id": "minecraft:magma_block"
  }
}