//class BlockHitboxed extends Block
private final AxisAlignedBB[] hitbox; //где то инициализируется
@Override
public void addCollisionBoxToList(
IBlockState state, World worldIn, BlockPos pos, AxisAlignedBB entityBox,
List<AxisAlignedBB> collidingBoxes, Entity entityIn, boolean isActualState) {
if(hitbox.length==1){
super.addCollisionBoxToList(
state, worldIn, pos, entityBox, collidingBoxes, entityIn,isActualState
);
} else {
for(AxisAlignedBB box:hitbox){
addCollisionBoxToList(pos, entityBox, collidingBoxes, box);
}
}
}