Well as you start off on the bank you already have most of the height you need.
As you throw yourself forward push all your weight down with the boat into the water.
As the boat reaches maximum pop upwards, you need to reach as high up as you can and roll yourself up into a tuck.
As soon as you have done this untuck and push your blades into the water as hard as you can.
The blades will be in the water at his stage and the boat will be airborne.
You will push the blades behind your head as you un-tuck yourself and the boat will loop fully!

Timing is key to this manoeuvre!