Need proof for functionality like slack.com

I need a new website. I need you to design and build my personal website. Hi., I need to create a sample demo page..for proving a concept .. dynamically creating subdomains. I would like you to go.. [login to view URL] and do signup.. it auto creates subdomains with our given unique name and also ..if you see.. how it handles redirection .. I want a similar kind functionality wise.. design not needed. Are they using any kind of framework or simply created by them?