How do I attach different volume to instance via Docker Machine API?

  amazon-ec2, docker, docker-machine

How developers attach different (besides "gp2") volume to EC2 instance using Docker Machine API ?
Given that they also use Docker Machine with docker compose to create containers ?

The docs say developer can use --volume-type "io1" but if you can’t supply the additional required argument iops that makes the flag little bit useless.

How developers go about this ?

Source: Docker Questions