The library natively supports InfoBox (a info window-like implementation). In order to render an info box instead of an info window, you just need to specify it on the info window:
use Ivory\GoogleMap\Overlay\InfoWindow;
use Ivory\GoogleMap\Overlay\InfoWindowType;
$infoWindow = new InfoWindow('content');
$infoWindow->setType(InfoWindowType::INFO_BOX);
Then, add it to your map and you're done!