Purchase a domain from Cloudflare beforehand and follow the guide to configure it.

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Verify Nginx Ingress Controller Hostname

To create a record in Cloudflare’s nameserver, check the IP of the Nginx Ingress Controller. 
kubectl get svc \
      -n ingress-nginx \
      ingress-nginx-controller \
      -o jsonpath='{.status.loadBalancer.ingress[0].ip}' \
  | xargs -I{} echo "{}"

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Create a Cloudflare Record

Navigate to DNS > Records page, click Add record and enter the values as shown below, then click Save.
  • Record Name: *
  • Record Type: A
  • Value: The retrieved Nginx Ingress Controller IP
  • Proxy Status: Disabled
You can verify that the record has been applied correctly with the following command:
dig "<domain registered as a record>"