app\ressources\views\form\coregistration.html.twig

{% block checkbox_widget %}
    <div class="checkbox_widget">
        {% set type = type|default('checkbox') %}
        {{ block('form_widget_simple') }}
    </div>
{% endblock %}

CoregistrationType.php

/**
 * On affiche une coche pour chaque coregistration
 */
$builder->addEventListener(
    FormEvents::PRE_SET_DATA,
    function (FormEvent $event) {
        /** @var CoregistrationVO $coregistration */
        $coregistration = $event->getData();
        $form = $event->getForm();

        $form->add(
            "accepted",
            CheckboxType::class,
            array(
                'label' => $coregistration->getSentence(),
                'attr' => array(
                    'class' => 'field-checkbox',
                    'logourl' => $coregistration->getLogoUrl()
                ),
                'required' => false,
            )
        );
    }
);

formTemplate.html.twig

{% form_theme form 'form/coregistration.html.twig' %}
{{ form_widget(formElement) }}

{# Ici formElement correspond à une checkbox #}