ExtraHoppers/src/main/resources/assets/extrahoppers/models/block/wood_hopper_side.json

{
  "parent": "block/hopper_side",
  "textures": {
    "particle": "block/oak_planks",
    "top": "block/oak_planks",
    "side": "block/oak_planks",
    "inside": "block/oak_planks"
  }
}