minecraft-kajetans-mod/src/main/resources/data/minecraft/recipes/lectern.json

{
    "type": "minecraft:crafting_shaped",
    "pattern": [
        "SSS",
        " B ",
        " S "
    ],
    "key": {
        "S": {
            "tag": "minecraft:wooden_slabs"
        },
        "B": {
            "tag": "km:bookshelf"
        }
    },
    "result": {
        "item": "minecraft:lectern"
    }
}