On top of adding attachments to your messages, you can also make your attachments interactive.
Take a look at this response on Slack:
This is how you would build that up
->setText('This is good!')
->addAction(Action::create('cool button', 'A Cool Button', 'button'))
Make sure you use the correct classes:
Take a look at Slacks documentation on interactive messages to learn what's possible. Please note that at this time only buttons are supported, and menus are not.