succession sequence sequential

I have seen many posts and guides on how to create a Signer Workflow which enables signing in sequence or succession. We have a requirement to allow our signers to sign at their own convenience in any order they choose. Can this be accommodated as well? If so, could someone please share the REST API code that would accomplish this so I may compare to our current json payload which has the signers indexed and is requiring succession signing ceremony. I have attached a snippet of code from the feature guide on Signer Workflow.