Set Up Subdomain System with Client Landing Page Template (DNS + Web)

I run a marketing agency and need a subdomain system set up on my existing domain (clientsconnect.net) so I can create individual subdomains for each of my clients (ex. sharpdetailing.clientsconnect.net). What I need: Subdomain system set up on clientsconnect.net so new subdomains can be created quickly for each client A simple reusable landing page template built that can be duplicated and customized per client — needs to look professional and include business name, service description, location, phone number and a contact button Each subdomain should load its own version of the landing page Clear instructions on how to add new subdomains and duplicate the template myself going forward