The working trot sitting is performed at the same tempo as the working trot posting –no slower. During the working trot sitting, the upper body is only a couple of degrees in front of the vertical. This nearly upright position allows your weight to sink into the horse’s back, so that you are firmly glued on and able to follow the motion with your seat and lower back.

Shown at the working trot sitting, Maria Schaub correctly keeps her upper body in the same position as at the walk, just a couple of degrees in front of the vertical.
To practice the sitting trot, drop your stirrups, pull the buckle on each stirrup down about six or eight inches, then cross the stirrup leathers over the horse’s withers. If you turn the top strip of the leather upside down before you cross it, your inner thigh won’t be resting on a lump that could bruise you.

The stirrup leathers are laid as flat as possible to prevent bruising the rider's thighs.
Your crotch should stay as close to the pommel as possible during this exercise, so that you are forked into the saddle with a secure thigh and knee position. (If you begin to slip backwards, grasp the pommel with one hand and adjust your position by pulling yourself forward.) Your calves should rest snugly against the animal’s sides, and the toes of your boots should be tipped upward as though you still had your feet in the stirrups. When working without stirrups at the sitting trot, then, your leg position should be exactly the same as it was when you had stirrups. Concentrate on relaxing your stomach and thigh muscles at the sitting trot so that you won’t bounce. Take a deep breath and let it out slowly, allowing your weight to sink downward. Remember, pinching at the thigh or tightening the stomach muscles draws you upward, away from the horse’s back, and causes great discomfort for both you and the horse.

Jessie Springsteen demonstrates how the rider can use both hands to adjust the seat forward at the sitting trot while being longed. If you have trouble slipping back in the saddle, having someone longe your horse while you work on your position can be very beneficial.