To understand the how the clutch works, I recommend this video.
Watch other videos too to have a better idea on how clutches work.
Many people fail the slope static test because they do not know the contact point of the clutch plates. Many people who failed make complaints such as the following.
"I already let go a lot of the clutch, the car just won't budge."
"I do not know how much clutch to let go."
"I'm afraid if I let go too much clutch, the engine will die."
and... my problem
"I let go too much clutch at the start and the car moved too fast forwards, not allowing me enough time to press the brake in time."
This is normal as we normally learn using a different car as the one we use for the driving test. Due to different amounts of wear and tear of the clutch plates, the point of contact for the pressure plates and flywheel is different. That's why people tend to let go too much or too little clutch.
There's a simpler method to overcome this problem.
1. The first thing you should do when you get on the test car is to check how much clutch is to be let go in order for the pressure plates to contact the flywheel. Once you get on the car, MAKE SURE THE HANDBRAKE IS LIFTED, switch on the engine and engage 1st gear. Let go the clutch slowly and notice when the car starts to rumble, showing that the car is about to breakdown. Let go a little more, and the car will breakdown. That's the point of contact of the pressure plates and flywheel. So as long as you don't let go beyond that point when your car is stationary, your engine shouldn't breakdown. REMEMBER THAT POSITION OF THE CLUTCH. That should be the position when your clutch plates are in partial contact, meaning that only a portion of the energy from the engine is transmitted to the wheels. You should be able to try this out several times before the instructor asks you to start. Play around with the clutch and if your engine breaks down, just restart the engine. They won't fail you as you haven't started the test yet.
2. When the instructor asks you to start, let got the clutch to the position where the clutch plates contact. Pump a little fuel and let go your handbrake. You car will move forwards smoothly.
3. As you approach the slope, let the inclination decelerate your car down. Then, when the car moves slow enough, pump in more gas. IF THE CAR DOESN'T ACCELERATE FORWARDS, REACT TO THE SITUATION AND RELEASE A LITTLE MORE CLUTCH. Your car should be moving slowly up the slope.
4. When you reach the yellow line, stop the car and free your gear.
5. Okay, now comes the important part, to move forwards from the slope. With the handbrakes lifted, accelerate the engine to 3 to 4 thousand rpm. Let go the clutch slowly and observe your rev meter closely. Once the rpm drops by 1 thousand, eg from 4k to 3k, maintain the level of clutch and let go the handbrake. Your car will move forwards so nicely as if you are a trained professional!
ps: Train using this method when you are practising with your driving instructor several times before you actually go for the test. DO NOT, I REPEAT, DO NOT TRY THIS FOR THE FIRST TIME ON THE DAY YOU SIT FOR THE TEST.