How can I create a plugin installation link?

Well, looks like I have found the answer. The action should be changed like so:

$action = 'install-plugin';
$slug = 'akismet';
wp_nonce_url(
    add_query_arg(
        array(
            'action' => $action,
            'plugin' => $slug
        ),
        admin_url( 'update.php' )
    ),
    $action.'_'.$slug
);

The answer was found in line 275 in the source code: https://core.trac.wordpress.org/browser/tags/3.9.1/src/wp-admin/includes/plugin-install.php