Pick up a piece of scrap metal (make sure it can bend) at a metal shop. Ours was cut to 42" x 16". Make sure to leave at least three extra inches so it can fold over the sides of the wood.
Cut the piece of wood to just two inches shorter than the length of your centerpiece. For a 42" x 10" centerpiece, cut the wood to 40".
Use a metal drill to pre-drill all holes where the black markers are placed.
Move the piece to a place where you can fully insert the screws so they are sticking out of the front of the metal. Finish by tightening the screws by hand. Be careful handling the centerpiece with the screws now exposed through the top.