Setup custom default backend for nginx ingress controller in Kubernetes - kubernetes

Question

I am stuck with custom default backend for error page from Nginx Ingress Controller. By default, Nginx Ingress Controller pods return Nginx's default page with errors such as 404, 50x and I want to modify them.
I have installed a DaemonSet of Nginx Ingress Controller following this tutorial. I use kubectl command to apply daemonset yaml file.
I found a tutorial from NGINX Annntations that show me setup a service that catching 404 error from ingress controller. I created a service following this Github repo. My Nginx Ingress Controller DaemonSet yaml file is:
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: nginx-ingress
namespace: nginx-ingress
spec:
selector:
matchLabels:
app: nginx-ingress
template:
metadata:
labels:
app: nginx-ingress
annotations:
nginx.ingress.kubernetes.io/custom-http-errors: "404,415"
nginx.ingress.kubernetes.io/default-backend: nginx-ingress/custom-default-backend
#prometheus.io/scrape: "true"
#prometheus.io/port: "9113"
#prometheus.io/scheme: http
spec:
serviceAccountName: nginx-ingress
containers:
- image: 10.207.149.80:80/smas/nginx/nginx-ingress:1.12.0
imagePullPolicy: IfNotPresent
name: nginx-ingress
ports:
- name: http
containerPort: 80
hostPort: 80
- name: https
containerPort: 443
hostPort: 443
- name: readiness-port
containerPort: 8081
- name: prometheus
containerPort: 9113
readinessProbe:
httpGet:
path: /nginx-ready
port: readiness-port
periodSeconds: 1
securityContext:
allowPrivilegeEscalation: true
runAsUser: 101 #nginx
capabilities:
drop:
- ALL
add:
- NET_BIND_SERVICE
env:
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
args:
- -nginx-configmaps=$(POD_NAMESPACE)/nginx-config
- -default-server-tls-secret=$(POD_NAMESPACE)/default-server-secret
It does not work :(
I also read Command-line Arguments tutorials and ConfigMap Resource tutorial but I do not see any argument/ config that allowing me to specify my custom defautl backend service.
Could you show me how to setup custom defautl backend service for my DaemonSet ?
Many thanks.