Keep practising.
My mum found the steepest possible hill in a 30 minute proximity of my house, I was forced to do 15 hill starts before dinner.
Biggest tip from me is keep a hand on the handbrake, as you hit the bite point, slowly release the handbrake. If you use this tip you should theoretically never roll back.
Just to explain this a bit more, come off of the clutch slowly, applying enough gas (with your hand/thumb pressing in the handbrake), then as you get to the bite point release push your thumb in and release the handbrake, come off of the clutch and accelerate.