Subtract Bounding Box

Hey,

i´ve got a small issue. I´m using Mcreator for 1.12.2 and getting an answer there is quite a thing. I want to create a corner block like the CR mod does. Unluckily the subtract bounding box option is bugged for the 1.12.2 generator in Mcreator and i can´t figure out what exact line of code i have to add in order to make it work.

This:

@Override
        public AxisAlignedBB getBoundingBox(IBlockState state, IBlockAccess source, BlockPos pos) {
            switch ((EnumFacing) state.getValue(BlockHorizontal.FACING)) {
                case SOUTH :
                default :
                    return new AxisAlignedBB(0, 0, 0, 0.5, 1, 1).union(new AxisAlignedBB(0, 0, 0, 0.5, 1, 1));
                case NORTH :
                    return new AxisAlignedBB(0.5, 0, 0, 1, 1, 1).union(new AxisAlignedBB(0.5, 0, 0, 1, 1, 1));
                case EAST :
                    return new AxisAlignedBB(0, 0, 0.5, 1, 1, 1).union(new AxisAlignedBB(0, 0, 0.5, 1, 1, 1));
                case WEST :
                    return new AxisAlignedBB(0, 0, 0, 1, 1, 0.5).union(new AxisAlignedBB(0, 0, 0, 1, 1, 0.5));

is the already manipulated code that gives the block a hitbox like it is a vertical half slab. But i want the hitbox to go around the corner. So i would either need a bounding box that is a standard block - the part that i want to cut out or a hitbox that just does the corner thing. What do i need to do?