How to manage remote workers?

Clearly defined work assignments with regular check in meetings to measure progress, give feedback, assess allocation of resources, etc. 

You are not qualified. Nor do you have such a job. Stop trolling.

How do you manage them when they are not remote?    What criteria do you use to determine whether they are performing adequately or not?   Make a list.  Then figure out how to monitor those benchmarks remotely.

You're making this more complicated than it is.  Either that, or you have zero management knowledge or experience.