As in, spin up volumes but not attach it to a VM and then be able to S/FTP to it…?
The closest one can get to such a setup is with volumes attached to on-demand VMs (viz. Apps v2 / Fly Machines). These Machines / VMs only spin up when there’s a request to be served (fly ssh console, for example) and then it is left up to the Machine’s / VM’s entrypoint process to determine when it must quit (docs).