Carlo

A drawing from Carlo. I find this fascinating. I assume that the victims hands are tied to the floor above the hole so she can't squat down, and won't be strong enough to lift herself up through the hole. With a much smaller aperture, it would take a more kinky turn.
The victim could be anybody as could the 'executioners', as could anyone who cared to watch.

Also from a spectacle point of view the victim has total lower body freedom so can jump, twist , do anything but alas they will never escape the whip.
From a safety point of view I would recommend a long whip, such as a dressage whip , and can see something similar in use. This will help prevent any contact between flailing legs and the 'executioner'. Also as the arse is so high , a longer instrument is needed to hit home. Unfortunately the longer the instrumnet the easier it is to inflict great pain.