Is there a way to create an aws ec2 instance with an existing volume or from an existing snapshot for the root volume? I’m using a volume attachment but it creates two volumes for the instance.

Use an EC2 snapshot to do this. EBS snapshots cannot be used directly for root volumes, afaik. Or you can create an EBS volume from an EBS snapshot, and then create the instance's root block device from the EBS volume.

You can’t provide an existing EBS volume as a root device. That’s part of my problem. I ended up creating a snapshot of the volume, creating an ami from that snapshot and using the ami to create the ec2 instance.