VanillaPlus/temp/blockmodels/vertical_polished_diorite_slab.json

{
  "parent": "vplus:block/vertical_slab",
  "textures": {
    "bottom": "minecraft:block/polished_diorite",
    "top": "minecraft:block/polished_diorite",
    "side": "minecraft:block/polished_diorite"
  }
}