etc/frontend/routes.xml
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:App/etc/routes.xsd">
<router id="standard">
<route id="smile_custom_entity" frontName="custom_entity">
<module name="Smile_CustomEntity" />
</route>
</router>
</config>