There's the pepakura template method. Basically, you make templates out of pepakura files and cut them out of foam, assemble them, and you're good to go.
Google "pepakura foam templates tutorial", the first three results are a three-part series on YouTube by TheHeroTutorials. Watch them and learn! Predator pepakura files can be found in this section of the forum, in the thread of Predator pepakura armor by movieman.