Sole juggles are one of the most tedious things to learn, go sit in a closed room because the ball is gonna go everywhere at first, hit the ball with the front part of the sole, you have to stay consistant on practicing, i agree with LIS throw it up with your feet other wise its just another step trying to learn that later, personally i learned sole stall first, but sole juggling is probably better to learn first so you get more familiar with it in both feet
just stay consistant on practicing, spend 20 straight minutes a day on it, and in about a week or 2 youll be able to sole juggle for a decent amount of time :D