Here's quick walkthrough how we run retrospectives using Trello boards. It's fairly simple workflow, and can be adapted with easy.

Few things to add,

• this approach turns out works well for both remote and in office environments;
• can be highly customized depends on needs;
• I haven't say that in video, but it's removes frictions with post-its, and use cards instead, and creates a possibilities to have issues to discuss in advance, prior to retrospective.

I'm using Playbook framework by Atlassian as an example for this board

If you have any questions, please let me know in comments below.