For many, including myself, Amazon Echo smart speakers and ... Amazon’s Alexa app can recognize when devices are ready to begin setup and will walk you through the process.
In its raw form, you could use a Dot as a supplementary Alexa portal, in addition to an Echo. You possibly wouldn't want to listen to music through it, unless perhaps you live in a monastery ...
Above that, the multifunction button can put Alexa in setup mode or activate the microphone ... In which case you might find the Amazon Echo Dot (4th Gen) makes more sense as it can be used ...