contacts-8.x-1.x-dev/layouts/tab_content_stacked/contacts-tab-content-stacked.html.twig

<div {{ attributes }}>
  <div class="dash-top">
    <div {{ region_attributes.top.setAttribute('data-contacts-manage-region-id', 'top') }}>
      {{ content.top }}
    </div>
  </div>
  <div class="dash-left">
    <div {{ region_attributes.left.setAttribute('data-contacts-manage-region-id', 'left') }}>
      {{ content.left }}
    </div>
  </div>
  <div class="dash-right">
    <div {{ region_attributes.right.setAttribute('data-contacts-manage-region-id', 'right') }}>
      {{ content.right }}
    </div>
  </div>
  <div class="dash-bottom">
    <div {{ region_attributes.bottom.setAttribute('data-contacts-manage-region-id', 'bottom') }}>
      {{ content.bottom }}
    </div>
  </div>
</div>