diff --git a/core/modules/field_layout/field_layout.install b/core/modules/field_layout/field_layout.install
index f3162b9..5956bf1 100644
--- a/core/modules/field_layout/field_layout.install
+++ b/core/modules/field_layout/field_layout.install
@@ -24,3 +24,19 @@ function field_layout_install() {
   // Invalidate the render cache since all content will now have a layout.
   Cache::invalidateTags(['rendered']);
 }
+
+/**
+ * Implements hook_uninstall().
+ */
+function field_layout_uninstall() {
+  // Reset each entity display to use the one-column layout to best approximate
+  // the absence of layouts.
+  $entity_save = function (EntityDisplayWithLayoutInterface $entity) {
+    $entity->setLayoutId('layout_onecol')->save();
+  };
+  array_map($entity_save, EntityViewDisplay::loadMultiple());
+  array_map($entity_save, EntityFormDisplay::loadMultiple());
+
+  // Invalidate the render cache since all content will no longer have a layout.
+  Cache::invalidateTags(['rendered']);
+}
diff --git a/core/modules/field_layout/src/Entity/FieldLayoutEntityDisplayTrait.php b/core/modules/field_layout/src/Entity/FieldLayoutEntityDisplayTrait.php
index 8d89d21..91cf936 100644
--- a/core/modules/field_layout/src/Entity/FieldLayoutEntityDisplayTrait.php
+++ b/core/modules/field_layout/src/Entity/FieldLayoutEntityDisplayTrait.php
@@ -45,6 +45,17 @@ public function getLayoutSettings() {
    * Implements \Drupal\field_layout\Display\EntityDisplayWithLayoutInterface::setLayoutId().
    */
   public function setLayoutId($layout_id, array $layout_settings = []) {
+    if ($this->getLayoutId() !== $layout_id) {
+      // @todo Devise a mechanism for mapping old regions to new ones in
+      //   https://www.drupal.org/node/2796877.
+      $new_region = $this->getLayoutDefinition($layout_id)->getDefaultRegion();
+      foreach ($this->getComponents() as $name => $component) {
+        if (isset($component['region']) && !isset($layout_regions[$component['region']])) {
+          $component['region'] = $new_region;
+          $this->setComponent($name, $component);
+        }
+      }
+    }
     $this->setThirdPartySetting('field_layout', 'id', $layout_id);
     $this->setThirdPartySetting('field_layout', 'settings', $layout_settings);
     return $this;
diff --git a/core/modules/field_layout/src/Form/FieldLayoutEntityDisplayFormTrait.php b/core/modules/field_layout/src/Form/FieldLayoutEntityDisplayFormTrait.php
index 9de90aa..b1256fb 100644
--- a/core/modules/field_layout/src/Form/FieldLayoutEntityDisplayFormTrait.php
+++ b/core/modules/field_layout/src/Form/FieldLayoutEntityDisplayFormTrait.php
@@ -162,40 +162,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
       $layout_plugin->submitConfigurationForm($form['field_layouts']['settings_wrapper']['layout_settings'], SubformState::createForSubform($form['field_layouts']['settings_wrapper']['layout_settings'], $form, $form_state));
     }
 
-    // If the layout is changing the regions will also change, update the
-    // placement of all fields.
-    if ($this->updateLayout($entity, $form_state)) {
-      // @todo Devise a mechanism for mapping old regions to new ones in
-      //   https://www.drupal.org/node/2796877.
-      $new_region = $entity->getDefaultRegion();
-      foreach ($form_state->getValue('fields') as $field_name => $values) {
-        if (($component = $entity->getComponent($field_name)) && $new_region !== 'hidden') {
-          $component['region'] = $new_region;
-          $entity->setComponent($field_name, $component);
-        }
-        else {
-          $entity->removeComponent($field_name);
-        }
-      }
-    }
-  }
-
-  /**
-   * Updates the entity with a new layout.
-   *
-   * @param \Drupal\field_layout\Display\EntityDisplayWithLayoutInterface $entity
-   *   The display entity.
-   * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current form state.
-   *
-   * @return bool
-   *   Returns TRUE if the layout has changed, FALSE if it is the same.
-   */
-  protected function updateLayout(EntityDisplayWithLayoutInterface $entity, FormStateInterface $form_state) {
-    $old_layout = $entity->getLayoutId();
-    $new_layout = $form_state->getValue('field_layout');
-    $entity->setLayout($this->getLayout($entity, $form_state));
-    return $old_layout !== $new_layout;
+    $entity->setLayout($layout_plugin);
   }
 
   /**
diff --git a/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php b/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
index 46ab6c2..1336a70 100644
--- a/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
+++ b/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
@@ -258,7 +258,7 @@ protected function getRegionTitles() {
    *   The machine name of the region.
    */
   protected function assertFieldInRegion($field_selector, $region_name) {
-    $region_element = $this->getSession()->getPage()->find('css', ".field-layout-region--$region_name");
+    $region_element = $this->getSession()->getPage()->find('css', ".layout-region--$region_name");
     $this->assertNotNull($region_element);
     $this->assertSession()->fieldExists($field_selector, $region_element);
   }
diff --git a/core/modules/field_layout/tests/src/Kernel/FieldLayoutEntityDisplayTest.php b/core/modules/field_layout/tests/src/Kernel/FieldLayoutEntityDisplayTest.php
index 09f1d79..a70ecdd 100644
--- a/core/modules/field_layout/tests/src/Kernel/FieldLayoutEntityDisplayTest.php
+++ b/core/modules/field_layout/tests/src/Kernel/FieldLayoutEntityDisplayTest.php
@@ -129,7 +129,10 @@ public function testPreSave() {
       'content' => [
         'foo' => [
           'type' => 'visible',
-          'region' => 'content',
+          'region' => 'main',
+          'weight' => -4,
+          'settings' => [],
+          'third_party_settings' => [],
         ],
       ],
       'hidden' => [
@@ -172,7 +175,10 @@ public function testPreSave() {
       'content' => [
         'foo' => [
           'type' => 'visible',
-          'region' => 'content',
+          'region' => 'main',
+          'weight' => -4,
+          'settings' => [],
+          'third_party_settings' => [],
         ],
       ],
       'hidden' => [
@@ -203,6 +209,9 @@ public function testPreSave() {
         'foo' => [
           'type' => 'visible',
           'region' => 'content',
+          'weight' => -4,
+          'settings' => [],
+          'third_party_settings' => [],
         ],
       ],
       'hidden' => [