A typical OnFrontiers consultation is online or over the phone. They usually last from 30 minutes to 1 hour. Follow up calls last 15+ minutes.
You get paid for your time on the phone and you get to set your own hourly rate. You can set and change your hourly rate in the settings: https://onfrontiers.com/settings/rate
Average hourly rates tend to be at $100, $160, $250 / hour, depending on years of industry experience and seniority.
Your hourly rate affects how many requests you get. But at the end of the day, you get to set whatever you feel is fair compensation for your time.