Step 1: Go to API Gateway, click Custom domain names.
Step 2: Click Create
Step 3: Enter the domain name and select the ACM Certificate. Use this to create a new public certificate. https://www.lazydeveloper.tech/aws/aws-certificate-manager-request-a-public-certificate/
Step 4: Click Create domain name
Step 5: Select the domain and click on API Mappings
Step 6: Click Configure API Mappings
Step 7: Click on Add new mapping
Step 8: Select the API and the appropriate Stage from the dropdown.
Step 9: Click Save
Step 10: Go to Route 53 -> Hosted Zones -> your custom domain
Step 11: Click Create record
Step 12: Select Simple routing
Step 13: Click Next -> Click Define simple record
Step 13: Enter the record name, select record type as A, select the API Gateway endpoint and click Define simple record
Step 14: Click Create records
