Page callback: Build the block instance add form.
string $plugin_id: The plugin ID for the block instance.
string $theme: The name of the theme for the block instance.
array The block instance edit form.
function block_admin_add($plugin_id, $theme) {
$entity = entity_create('block', array(
'plugin' => $plugin_id,
'theme' => $theme,
));
return entity_get_form($entity);
}