Here's a link to my RESTful API Boilerplate built on Slim 3 - https://github.com/dupkey/slim3-api
More info in the README. Any feedback is greatly appreciated. Let me know if my code could be better or if any of my comments here are off-base.
My Experience with Slim 3
I like how Slim 3 works well with the ADR (Action-Domain-Responder) pattern.
There are some nice helper functions like setArguments which aided me in passing args to middleware!
The documentation has come a long ways recently and the doc search is super helpful.
This is more of a gripe about Pimple but I wasn't able to wire my dependencies into a Base Action and then extend that action. I know that Aura.Di allows you to inherit constructor parameters but I couldn't get Aura working in Slim without errors. (Specifically: cannot modify container when locked. Following this tutorial: https://blog.shameerc.com/2015/09/slim-3-replacing-pimple-with-auradi)
I wasn't able to "setArguments" in my route groups which would have simplified things slightly as I wouldn't have to set the same argument on four routes within a group.