Below are the steps of build a custome VPC:

1. Create a VPC
2. Create subnets
3. Create an internet gateway (IGW)
4. Attach the new IGW to your VPC
5. Create a new route table (RT)
6. Add the IGW as a route to the new RT
7. Add a subnet to the RTs subnet associations (this will be the PUBLIC facing subnet)
8. Create web server (public subnet) and database server (private subnet) instances
9. Create a new security group for the NAT instance
10. Add HTTP and HTTPS inbound rules that allow traffic from the private subnets IP
11. Create a NAT instance (public subnet).

• Community AMIs.
• Search for amzn-ami-vpc-natChoose the FIRST IMAGE.
• Diable Auto-assign Public IP.
• Add it to the NAT security group

12. Create an ELASTIC IP
13. Associate the Elastic IP to the NAT
14. Disable Source/Destination Checks for the NAT
15. Add the NAT instance as a route to the initial VPC RT

Below are the steps of build a custome VPC:

12. Create an Elastic IP
13. Associate the Elastic IP to the NAT
14. Disable Source/Destination Checks for the NAT
15. Add the NAT instance as a route to the initial VPC RT