Step 3: Clamp the plastic

Picture of Clamp the plastic
Place the plastic between two bits of metal and clamp them in the vice, the thinner piece will be what you are folding the plastic over (so its thickness will become the depth of the bend) and the thicker one at the back acts as a heat shield
you're going to do the smaller bend first that's the one on the inside of the clip.
Make sure you have clamped the plastic square (at a right angle) to the metal that's holding it.