One-leg squat, training wheels on.
Use the straps only for balance, let the standing leg do the work.
The pistol squat asks one quad to lower and lift your entire bodyweight through the deepest squat range there is, and the straps exist so you can actually train that instead of falling over trying. Working strictly one leg at a time, the glutes control the hip through the deep bottom position while light strap tension keeps you balanced and honest. It earns its place as the standard route to a free pistol, letting you grease the full movement from day one and slowly retire the assistance.
That is exactly what it is for. The straps handle balance and offer a light assist out of the hole, so you can train the full-depth pattern immediately and gradually reduce how much you pull.
As little as gets you moving. Use light tension through the sticking point at the bottom, and over the weeks aim for straps so slack they are barely more than a handrail.
Holding the free leg out demands hip flexor strength and hamstring flexibility most people have not built yet. Keep practising, and let it bend slightly rather than letting it touch down.
