I do this with Route53. Create a hosted zone with your subdomain - R53 will populate NS records automatically. Then, go back to your top-level zone and add those NS records for the subdomain.
After a little research, I was also able to discover FreeDNS from Namecheap (https://www.namecheap.com/domains/freedns/). Once I set up 5 NS records in my main zone for my subdomain and waited a half a day, the subdomain's DNS records were manageable from my Namecheap dashboard.
After a little research, I was also able to discover FreeDNS from Namecheap (https://www.namecheap.com/domains/freedns/). Once I set up 5 NS records in my main zone for my subdomain and waited a half a day, the subdomain's DNS records were manageable from my Namecheap dashboard.