ext_tables.php

<?php
if (!defined('TYPO3_MODE')) {
	die ('Access denied.');
}

TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile($_EXTKEY, 'Configuration/TypoScript', 'My provider extension');
\FluidTYPO3\Flux\Core::registerProviderExtensionKey('myprovider', 'Page');
\FluidTYPO3\Flux\Core::registerProviderExtensionKey('myprovider', 'Content');

Layouts-Content.html

<f:layout name="Content" />
<f:render section="Main" />

Templates-Content-Example.html

{namespace flux=FluidTYPO3\Flux\ViewHelpers}
<f:layout name="Content" />

<f:section name="Configuration">
	<flux:form id="fluidfluxcontent" label="Fluid/FluxContent" options="{icon: 'Icons/Content/Example.gif'}">
		<!-- Insert fields, sheets, grid, form section objects etc. here, in this flux:flexform tag -->
	</flux:form>
</f:section>

<f:section name="Preview">
	<!-- uncomment this to use a grid for nested content elements -->
	<!-- <flux:widget.grid /> -->
</f:section>

<f:section name="Main">
	<h3>I am a content element!</h3>
	<p>
		My template file is EXT:myprovider/Resources/Private/Content/Example.html.
	</p>
</f:section>