These are the most comfortable leggings with pockets I have ever found. They stretch just right so they are long enough for me and they feel amazing. They stay in place on the stomach and don't roll or slide down. The pocket is large enough to fit my Samsung s8 + and was easy to slide it in and out. I defently recommend these and plan to get more.
https://www.amazon.com/Picotee-Workout-Running-Fitness-Leggings/dp/B076SSVBKV