Instantiate and load a block programmatically in twig template
I am sure there are other ways to solve this problem, but here is how I would do it.  

Create your block, then go to admin/structure/block and place your block under "Disabled" list. You can then implement hook_preprocess_node in your .theme.php file.

theme file:

/**
 * Implements hook_preprocess_node()
 */

function mytheme_preprocess_node(&amp;$variables) {
 $block = \Drupal\block\Entity\Block::load('block_id');
  if ($block) {
    $variables['my_custom_block'] = \Drupal::entityTypeManager()-&gt;getViewBuilder('block')-&gt;view($block);
  }
}


In your template twig file:

{% if my_custom_block %}
 {{ my_custom_block }}
{% endif %}


You just have to make sure that your block_id correct.