BiomesOPlenty/src/main/resources/assets/biomesoplenty/models/block/orange_sandstone_slab_top.json

{
    "parent": "block/slab_top",
    "textures": {
        "bottom": "biomesoplenty:block/orange_sandstone_bottom",
        "top": "biomesoplenty:block/orange_sandstone_top",
        "side": "biomesoplenty:block/orange_sandstone"
    }
}