I'm not sure I like AWS CloudFormation (CF). Beside the obvious lock-in I currently would rather use TerraForm or similar to describe what infrastructure I want. However CF will always have the most complete features especially for new AWS services, so it's probably good to know. And one day you'd possibly have to modify a CF configuration file, so it's a really good thing to know if you work with AWS.

Anyway, my observations:

1. I do not recommend to use JSON for CF. Use YAML. It's much shorter and much easier to read. I usually like JSON, but here it's outclassed by YAML.
2. As a PowerUser, to use CF you need some extra permissions:
   1. iam:CreateInstanceProfile
   2. iam:DeleteInstanceProfile
   3. iam:PassRole
   4. iam:DeleteRole
   5. iam:AddRoleToInstanceProfile
   6. iam:RemoveRoleFromInstanceProfile

Here are the command lines to use:

aws cloudformation create-stack --template-body file://OneEC2AndDNS.yaml --stack-name OneEC2 \
--parameters ParameterKey=InstanceType,ParameterValue=t2.nano --capabilities CAPABILITY_IAM

To see what was created (takes about 4 min 20 sec):

aws cloudformation describe-stacks --stack-name=OneEC2-6

gives you this output (some data replaced by X):

aws cloudformation describe-stacks --stack-name=OneEC2-6
    "Stacks": [
        {
            "StackId": "arn:aws:cloudformation:ap-northeast-1:XXXXXXXXXXXX:stack/OneEC2-6/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX", 
            "Description": "Build EC2 instance with current AWS Linux and create a DNS entry in aws.qw2.org", 
            "Parameters": [
                {
                    "ParameterValue": "aws.qw2.org", 
                    "ParameterKey": "HostedZone"
                }, 
                {
                    "ParameterValue": "t2.nano", 
                    "ParameterKey": "InstanceType"
                }
            ], 
            "Tags": [], 
            "Outputs": [
                {
                    "Description": "Fully qualified domain name", 
                    "OutputKey": "DomainName", 
                    "OutputValue": "i-034dcbb1c60d1e062.ap-northeast-1.aws.qw2.org"
                }
            ], 
            "CreationTime": "2018-03-11T12:57:50.851Z", 
            "Capabilities": [
                "CAPABILITY_IAM"
            ], 
            "StackName": "OneEC2-6", 
            "NotificationARNs": [], 
            "StackStatus": "CREATE_COMPLETE", 
            "DisableRollback": false, 
            "RollbackConfiguration": {}
        }
    ]
}

And to delete it all (takes about 3 min 30 sec):

aws cloudformation delete-stack --stack-name=OneEC2-6