Simple Custom Layout (#Accounts/layout/my-layout)

my-layout.php

<?php
//custom/modules/Accounts/clients/base/layouts/my-layout/my-layout.php
$viewdefs['Accounts']['base']['layout']['my-layout'] = array(
    'components' => array(
        array(
            'view' => 'my-view',
        )
    )
);

my-view.js

//custom/modules/Accounts/clients/base/views/my-view/my-view.js
({
    _render: function() {
        this.$el.html("Hello World!");
    }
})