The motion the giver performs is similar to that of Side Rider; happily, Riding Astride requires less physical exertion on the receiver’s part, which facilitates longer playtime - not to mention uninterrupted stimulation! For the giver - well, they just lay there!
The giver lays back on a couch or low bed while the performing partner, who's facing away, situates themselves perpendicularly to the giver and squats down on them.
Although our animation shows the performer with legs closed, they can also open them up and lean forward, using the couch edge to brace themselves. Another variation is for the performer to place their hands behind them against the couch back; this way, their hips and abs can do the work. Both of these adaptations will change the angle of penetration and give the legs a needed rest.