bedrock-samples/behavior_pack/recipes/composter_from_mangrove_slab.json

{
    "format_version": "1.16",
    "minecraft:recipe_shaped": {
        "description": {
            "identifier": "minecraft:composter_from_mangrove_slab"
        },
        "tags": [
            "crafting_table"
        ],
        "pattern": [
            "A A",
            "A A",
            "AAA"
        ],
        "key": {
            "A": {
                "item": "mangrove_slab"
            }
        },
        "result": {
            "item": "composter",
            "count": 1
        },
        "priority": 2
    }
}