--- /dev/null
+<?php
+
+namespace Drupal\block\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+
+/**
+ * Controller for building the block instance add form.
+ */
+class BlockAddController extends ControllerBase {
+
+ /**
+ * Build the block instance add form.
+ *
+ * @param string $plugin_id
+ * The plugin ID for the block instance.
+ * @param string $theme
+ * The name of the theme for the block instance.
+ *
+ * @return array
+ * The block instance edit form.
+ */
+ public function blockAddConfigureForm($plugin_id, $theme) {
+ // Create a block entity.
+ $entity = $this->entityManager()->getStorage('block')->create(['plugin' => $plugin_id, 'theme' => $theme]);
+
+ return $this->entityFormBuilder()->getForm($entity);
+ }
+
+}