The main key here is stealing.
You want to knock the ball loose and dive for it with the

button. Obviously the best case is you knock the ball from the opposing basket towards your basket.
If you manage to get the ball on the dive, you will end up in a seated position with the ball. If you think you are close enough, take the shot. I've taken a few shots while seated now and have not sensed any timing or skill too it.
I just got lucky and the first one I ever tried made it.
Good luck!