If I were to create a pie launcher, it would be more like the pie pod launchers.
It seems pretty easy to construct. Just a base, and attach to that a hinge. That hinge holds a rake, which is also connected to the base with a spring. Further up the rake is a lock, that you use to secure the rake down. When it's ready to fly, release the lock.
I'm actually in the process of engineering something that'll add a whole new level of amusement to my production. Not a pie launcher but something super amusing