TYPO3 - Extension flexform storage in entity - typo3

Question

On Typo3 6.2, I have an extension with :
an Entity "Event"
several properties : "name", "location", "date", "description"
a plugin ("event_plugin") and a flexform
My goal is to allow the backend users to create events by adding the plugin on any page and then configure the properties via flexform (or similar).
I note the datas from the flexform are stored in database on the tt_content table, inside the "pi_flexform" column ... but what I would like is to use my entity system without creating any backend module !
I guess it's possible because some existing extensions are developed this way (powermail...)
EDIT : a little more code/details about my question :
My entity "Event" :
<?php
namespace MyCompany\MyCompanyevents\Domain\Model;
class Event extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
{
/**
* name
*
* #var string
*/
protected $name = ''
/**
* eventdate
*
* #var integer
*/
protected $eventdate = 0;
/**
* eventlocation
*
* #var string
*/
protected $eventlocation = '';
/**
* eventdescription
*
* #var string
*/
protected $eventdescription = '';
// ALL the setters and the getters
}
?>
My Controller :
<?php
namespace MyCompany\MyCompanyevents\Controller;
class EventController extends \TYPO3\CMS\Extbase\Mvc\Controller\ActionController
{
/**
* eventRepository
*
* #var \MyCompany\MyCompanyevents\Domain\Repository\EventRepository
* #inject
*/
protected $eventRepository = NULL;
/**
* action list
*
* #return void
*/
public function listAction() {
$events = $this->eventRepository->findAll();
$this->view->assign('events', $events);
}
// Other Actions generated by the Extension builder : add, edit, update, delete, show
}
?>
My plugin works, and I know how to link a flexform file.
With some TCA configuration, the backend users may already create event one by one wherever they want. What I'm looking for is to link a flexform file to my plugin which would allows the users to create an event and fill all the details (name, location etc...) directly into the plugin.
This way, the plugin should look like :
.. and save the plugin would save a new Event instance in database.