Where to put ball for psoas release?

I'm curious, could you elaborate on where exactly one should place a ball for psoas release? Is there a specific area of the body that targets this muscle group most effectively? Are there any precautions or techniques that should be kept in mind when performing this type of self-massage? Additionally, are there any alternative methods or exercises that can also help to release tension in the psoas muscles? I'd appreciate any guidance or insights you can provide on this topic.