Start approaching to the turn by going left , and just before the beggining of the turn
press RIGHT key. As you start making the corner, you now need to press BRAKE, which means you will be pressing 3 keys at the same time : GAS, RIGHT, BRAKE. You will now be sliding accross the turn.
And what to do next?? simply release brake button, the car will continue to slide even if you
are not pressing the BRAKE key.
In this demonstration, i release at middle of the turn both GAS and BRAKE key.
but the RIGHT key stays pressed all the time till the finish!!
Important : It doesnt mean that you will always have to release the GAS key. I just did that to control the speed of the car, wich can also be compensated by pressing longer on the BRAKE key instead of releasing GAS. It always depends on the angle of the turn, total speed you were driving, and preparations for approach on a possible next turn.