Create Instance in us-east-1c --> Configure Instance Details is missing

Hello.

The "Configure Instance Details" setting mentioned in the AWS re:Post Agent answer does not exist when launching an instance.
I think this is an incorrect answer.
EC2 is a resource that runs on a subnet.
Subnets are associated with availability zones, so create a subnet associated with the availability zone in which you want to launch your instance.
When launching an EC2 instance, you can select a subnet in the "Network settings" section.
When selecting a subnet, I think this can be resolved by selecting the subnet for the Availability Zone in which you want to launch the instance.

To specify the exact availability zone when launching an EC2 instance, such as us-east-1c, you need to follow these steps:

1. Open the Amazon EC2 console and start the instance launch process.

2. Select your desired AMI and instance type as usual.

3. In the "Configure Instance Details" section, you should see an option to choose the availability zone. If you don't see this option, it's possible that your account doesn't have default subnets in all availability zones for the us-east-1 region.

To resolve this and ensure you can launch in us-east-1c:

1. Use the AWS CLI to check available availability zones in your account for the us-east-1 region with this command: aws ec2 describe-availability-zones --query 'AvailabilityZones[].ZoneName' --region us-east-1

2. If us-east-1c is not listed or you don't see default subnets, you can create one using: aws ec2 create-default-subnet --availability-zone us-east-1c --region us-east-1

3. After creating the default subnet, you should be able to see and select us-east-1c in the EC2 launch wizard.

Remember, to attach an existing EBS volume to your new instance, both the volume and the instance must be in the same availability zone. If your existing volume is in us-east-1c, make sure to launch your new instance in us-east-1c as well.

If you've already launched the instance in us-east-1a and need to move it, you'll need to create a new instance in us-east-1c and then attach the volume to that new instance. You cannot move an existing EC2 instance between availability zones.
Sources
can not run this cloudform at my account in region us-east-1 | AWS re:Post
Adding an existing volume to new Instance | AWS re:Post