725's technique can also be done against a belt or even your leg (with enough force), I've done that for 1-handed reloading drills since I was taught it many years ago. Rear sight, not the front, is where you put the pressure, and point muzzle in a safe direction please

My sister couldn't rack the slide at first, she was given 10 bazillion 2-handed racks as homework and strengthened her arms up fast!