Here are a couple of videos posted on YouTube by Mario Proulx showing his side bender and how he bends sides. The bender and his method are about as simple as it gets. Even I might be able to make a side bender like this one.
Here are links to two videos. The first one he bends the side and in the second one he removes the side and places it right into the mold. He wants a little springback in the waist so the side fits to the mold nicely.
Bending the Sides
Transferring Sides to the Mold