Webinar starting practice session only by the host?

We have a webinar license and always use the practice session before allowing the audience in. Up to now, only the host can open the practice session while the panelists are directly put on a waiting list until the host is online. How can we prevent this and allow the panelists to open the practice session themselves? This is very useful as the host cannot always be available.

Please describe the procedure to do it this way. I hope it's possible.

Thanks