>>22027140

>Can someone explain the exercise to develop these side upper leg muscles?

Keeping your feet towards the bottom of the footpad and your legs closer together shifts the emphasis away from the glutes and hamstrings and into the outer quads to build an impressive quad sweep.

https://liftvault.com/exercises/outer-quad-exercises/

>>22027311

>What exercise specifically builds that area to flare out?

10 exercises to build hip muscles. Here are some of my favorite hip exercises that can help strengthen and sculpt your hips.

https://www.healthline.com/health/fitness-exercise/how-to-get-wider-hips