Single-leg squat with the other ankle crossed in a figure-4.
Use the straps only for balance, let your working leg do the real work.
Crossing one ankle over the opposite knee and squatting on the remaining leg gives the working quad a full single-leg challenge while the crossed position adds a deep stretch through the outside of the folded hip. The glute of the standing leg assists the drive up and keeps the pelvis level over one foot the whole set, since this is strictly one side at a time. It earns its place as strength and hip mobility in one rep, a single-leg squat that stretches the very hip most lifters need opened.
Crossing the ankle over the knee stretches the outside of that hip while you squat, so you load the standing leg and mobilise the folded one simultaneously. Two jobs, one exercise.
As deep as you can with a tall chest and controlled descent. The straps are your safety net for depth, but the working leg should still handle the actual lifting.
Single-leg squats expose hip weakness fast. Slow down, push the knee in line with your toes, and use a touch more strap support until the wobble steadies out.
