The Stuff You'll need: Coroplast Sheet, heat gun, 2-2.5 by 1. 5 slotted steel angles 6 to 8 feet long
Pinch the Coroplast Sheet between the two slotted angles. Bolt down the angles to each other and put super magnets on the sides of the steel pinching the sheet so they attract and squeeze the sheet in the middle, where the angles tend to bend . Then put a bending force in the way you want the sheet to bend.
Step 2: Underneath the Sheet With the Heat Gun
Above all be safe and try to be ventilated. The heat process won't take long. Start at end of the jig that has the least bending force on it. If the bending forces are equal, start heating in the middle and work out evenly. After very little time the inner layer will start to expand and push outward. Try not the get one part of the sheet heated more than another, although the metal angle will spread the heat more evenly. You can lay down the sheet when the inner sheet is evenly folded, and it should fold neatly with a pop.
Step 3: Done
Above all this is both tech and art form. Have fun