Rob Allen has a quick post showing how to use Eloquent in a Slim framework application to work with your database queries and functionality.

Eloquent is one of the easier ORMs to get started with, so let's look at how to use and test it within a Slim Framework application. [...] Eloquent is quite a nice implementation of the Active Record pattern. If that meets your needs, then it is easy to use within a Slim Framework application, so go for it!

He walks you through the set up of the Eloquent package via a Composer require and update your Slim configuration with the database settings. He then includes the few lines you'll need to use the "capsule" manager to integrate it with the Slim structure. He also talks about testing models and shows how to create some simple tests with PHPUnit and a bit of mocking.