These pun-laden titles have got to stop.
To start the grill, I cut out a simple rectangle. Optimus Prime has a rectangular notch at the bottom of his grill and grill lines above it which are divided into two sections. As you can see on the right, I cut out these two sections as well as the large section at the bottom. Since the bottom section is inset a little, I shaved the piece of styrofoam down with the utility knife.
Next, I sliced the rectangular sections that will make the grill lines into neat 1 inch by 1/2 inch pieces. I then bevelled what would be the top edge of each to make the grill look more three dimensional.
Here's a final image of the grill with all of the pieces inserted.