How to design flexible software

We previously held a fishbowl about how to design to avoid configuration. But when you can't avoid configuration, how do you do it well? And if we want our software to be flexible, what other options do we have besides configuration? What other ways are there to make software flexible?

This is a fishbowl: a panel conversation held on the Handmade Network Discord where a select few participants discuss a topic in depth. We host them on a regular basis, so if you want to catch the next one, join the Discord!