diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
index 474c654..f12f87d 100644
--- a/core/modules/block/templates/block-list.html.twig
+++ b/core/modules/block/templates/block-list.html.twig
@@ -13,11 +13,11 @@
  * @ingroup themeable
  */
 #}
-<div class="layout-block-list clearfix">
-  <div class="layout-region block-list-primary">
+<div>
+  <div>
     {{ form|without('place_blocks') }}
   </div>
-  <div class="layout-region block-list-secondary">
+  <div>
     {{ form.place_blocks }}
   </div>
 </div>
diff --git a/core/modules/block/templates/block.html.twig b/core/modules/block/templates/block.html.twig
index 2680121..3a32d75 100644
--- a/core/modules/block/templates/block.html.twig
+++ b/core/modules/block/templates/block.html.twig
@@ -33,13 +33,7 @@
  * @ingroup themeable
  */
 #}
-{%
-  set classes = [
-    'block',
-    'block-' ~ configuration.provider|clean_class,
-  ]
-%}
-<div{{ attributes.addClass(classes) }}>
+<div>
   {{ title_prefix }}
   {% if label %}
     <h2{{ title_attributes }}>{{ label }}</h2>
diff --git a/core/modules/block_content/templates/block-content-add-list.html.twig b/core/modules/block_content/templates/block-content-add-list.html.twig
index e5a5d97..0810461 100644
--- a/core/modules/block_content/templates/block-content-add-list.html.twig
+++ b/core/modules/block_content/templates/block-content-add-list.html.twig
@@ -15,7 +15,7 @@
  */
 #}
 {% spaceless %}
-  <dl class="node-type-list">
+  <dl>
     {% for type in types %}
       <dt>{{ type.link }}</dt>
       <dd>{{ type.description }}</dd>
diff --git a/core/modules/block_content/templates/block-content-add-list.html.twig b/core/themes/classy/templates/block-content-add-list.html.twig
similarity index 100%
copy from core/modules/block_content/templates/block-content-add-list.html.twig
copy to core/themes/classy/templates/block-content-add-list.html.twig
diff --git a/core/modules/block/templates/block-list.html.twig b/core/themes/classy/templates/block-list.html.twig
similarity index 100%
copy from core/modules/block/templates/block-list.html.twig
copy to core/themes/classy/templates/block-list.html.twig
diff --git a/core/modules/block/templates/block.html.twig b/core/themes/classy/templates/block.html.twig
similarity index 100%
copy from core/modules/block/templates/block.html.twig
copy to core/themes/classy/templates/block.html.twig