Making blocks directional (facing into certain directions) is also done using block states. This example describes a vertical version of the andesite slab.

public class VerticalSlabBlock extends HorizontalFacingBlock {
 
	public VerticalSlabBlock(Settings settings) {
		super(settings);
		setDefaultState(this.stateManager.getDefaultState().with(Properties.HORIZONTAL_FACING, Direction.NORTH));
	}
 
	@Override
	protected void appendProperties(StateManager.Builder<Block, BlockState> stateManager) {
		stateManager.add(Properties.HORIZONTAL_FACING);
	}
 
	@Override
	public VoxelShape getOutlineShape(BlockState state, BlockView view, BlockPos pos, ShapeContext ctx) {
		Direction dir = state.get(FACING);
		switch(dir) {
			case NORTH:
				return VoxelShapes.cuboid(0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.5f);
			case SOUTH:
				return VoxelShapes.cuboid(0.0f, 0.0f, 0.5f, 1.0f, 1.0f, 1.0f);
			case EAST:
				return VoxelShapes.cuboid(0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f);
			case WEST:
				return VoxelShapes.cuboid(0.0f, 0.0f, 0.0f, 0.5f, 1.0f, 1.0f);
			default:
				return VoxelShapes.fullCube();
		}
	}
 
        @Override
	public BlockState getPlacementState(ItemPlacementContext ctx) {
		return (BlockState)this.getDefaultState().with(Properties.HORIZONTAL_FACING, ctx.getPlayerFacing().getOpposite());
	}
 
}

src/main/resources/assets/tutorial/blockstates/polished_andesite_side_block.json

{
  "variants": {
    "facing=north": { "model": "bitmod:block/polished_andesite_side_block", "uvlock": true },
    "facing=east":  { "model": "bitmod:block/polished_andesite_side_block", "y":  90, "uvlock": true },
    "facing=south": { "model": "bitmod:block/polished_andesite_side_block", "y": 180, "uvlock": true },
    "facing=west":  { "model": "bitmod:block/polished_andesite_side_block", "y": 270, "uvlock": true }
  }
}

src/main/resources/assets/tutorial/models/block/side.json

{   "parent": "block/block",
    "textures": {
        "particle": "#side"
    },
    "elements": [
        {   "from": [ 0, 0, 0 ],
            "to": [  16, 16, 8 ],
            "faces": {
                "down":  { "texture": "#bottom", "cullface": "down" },
                "up":    { "texture": "#top",    "cullface": "up" },
                "north": { "texture": "#side",   "cullface": "north" },
                "south": { "texture": "#side",   "cullface": "south" },
                "west":  { "texture": "#side",   "cullface": "west" },
                "east":  { "texture": "#side",   "cullface": "east" }
            }
        }
    ]
}

src/main/resources/assets/tutorial/models/block/polished_andesite_side_block.json

{
    "parent": "tutorial:block/side",
    "textures": {
        "bottom": "block/polished_andesite",
        "top": "block/polished_andesite",
        "side": "block/polished_andesite"
    }
}

For directional blocks, you may have to override rotate and mirror methods, so that in structure blocks, they can be correctly rotated or mirrored.