ot_typo3/ot_templating/Resources/Private/Layouts/Backend/Default.html

{namespace v=FluidTYPO3\Vhs\ViewHelpers}

<f:be.container includeCssFiles="{ot_core: '{f:uri.resource(path:\'assets/Backend/style/ot_be_module.css\', extensionName:\'ot_core\')}',
                                  ot_customizer: '{f:uri.resource(path:\'assets/Backend/style/ot_customizer.css\')}'}">
    <f:render section="content" />
</f:be.container>