Create custom Logger file in Magento 2

di.xml

<!-- Location:  app/code/JLNarvaez/CustomLog/etc/di.xml -->

<?xml version="1.0"?>
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
     xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
     <!-- ... -->
     <!-- ... -->
     <!-- ... -->
     
     <type name="JLNarvaez\CustomLog\Logger\Handler">
         <arguments>
             <argument name="filesystem" xsi:type="object">Magento\Framework\Filesystem\Driver\File</argument>
         </arguments>
     </type>
     <type name="JLNarvaez\CustomLog\Logger\Logger">
         <arguments>
            <!-- Nombre que tendrá el Logger (aparecerá en el fichero .log cuando se escriba algun log) -->
             <argument name="name" xsi:type="string">myCustomLog</argument> 
             <argument name="handlers"  xsi:type="array">
                <!-- Namespace de nuestro Handler -->
                 <item name="system" xsi:type="object">JLNarvaez\CustomLog\Logger\Handler</item> 
             </argument>
         </arguments>
     </type>
     
     <!-- ... -->
     <!-- ... -->
     <!-- ... -->
 </config>

Handler.php

// Location: app/code/JLNarvaez/CustomLog/Logger/Handler.php

<?php
namespace JLNarvaez\CustomLog\Logger;

use Monolog\Logger;

class Handler extends \Magento\Framework\Logger\Handler\Base
{
    /**
     * Logging level
     * @var int
     */
    protected $loggerType = Logger::INFO;

    /**
     * File name
     * @var string
     */
    protected $fileName = '/var/log/jlnarvaez_custom.log';
}

Logger.php

// Location: app/code/JLNarvaez/CustomLog/Logger/Logger.php

<?php
namespace JLNarvaez\CustomLog\Logger;

class Logger extends \Monolog\Logger
{
}