A side plank or a side balance on the BOSU ball is pretty simple. It's just the same thing you would do on the floor, but on a BOSU ball.
So either your hand comes down, or your elbow. You want it right in the middle. If you have wrist issues or shoulder issues, I would definitely recommend staying on your elbow and not on your hand. And what you do is put your body into a plank position. If you want, you can extend your arm. Now, if this is too difficult for you, what you could do is you could put one foot in front of you and hold it up, and just get a little practice holding that plank position, you know, until you can bring yourself all the way up.
And then, if you wanted to make it more difficult, you can bring one leg up, you can grab one foot and pull it back, or you can even do little dips. And so if you're going to do the dips, you want to be on your elbow. You're in plank position, one foot in front of the other, and you dip your hips in and then you push them back in. And you dip them back in, and you push them back. You'll start to feel that in the oblique.
That would be a side balance or a side plank on the BOSU ball.