The raised rpm/clutch slip launch method involves raising the rpm's while simultaneously slipping(slowly releasing) the clutch. When done correctly the engine doesn't bog, and the tires spin only a few feet. Then, once the tires grab traction the gas pedal is quickly and smoothly pressed to the floor(Don't stab it). The key is to go WOT as quickly as possible from a standstill without bogging or excessive spinning.
The rpm level and amount of clutch slip during launch is a trial-and-error process that depends mostly on the traction capacity of your tires' and the track, and the DA(ambient temp, humidity, altitude).
Suggest you also experiment with rear tire pressures. Lowering it may increase traction.
Also, stay out of the water box if possible with street tires.