Cut a piece of lattice to the height and width you want the headboard. Use a circular saw. Lay the lattice on a flat surface.
Select four pieces of half round, 1 inch mitered molding that match the length of the four sides of the lattice. Apply a bead of wood glue to the back of each piece of molding. Press the molding onto the front edges of the lattice so the mitered edges line up. Let the glue dry for 24 hours.
Use the wood glue to glue three picture frame hooks to the back of the lattice. Glue them to the top edge. Put one on each side and one in the middle.
Put the headboard in place behind the bed. Have a helper hold it up, if you want it off the floor. Mark the spot on the wall where the hooks touch the wall.
Hammer one nail into each marked spot. Hang the lattice in place from the hooks.