Draw the shape of the back panel on the top half of the plywood. The ends and bottom will be rectangular while the top is rounded. Assuming you're making a headboard for a standard queen size bed, you can make the width 66 inches. The height of the back panel can be 44 inches.
Draw the wings on on lower half of the plywood. The wings need to match, therefore, it might be helpful to use paper to draw and cut out a template and transfer it to the plywood. The wings will be approximately 54 inches tall and 12 inches wide. The top should curve out wider than the bottom.
Cut the back panel and wings out with a jigsaw. Sand the edges to prevent snagging the foam or material. Hold the wings in place on the back panel. Measure and mark screw holes, starting at the point where the wings will attach prior to upholstering. Drill four holes, starting 1 inch from the top and spaced every 10 inches.
Trace the plywood pieces onto foam. Use a utility knife to cut out the foam.
Cut out the fabric to cover each section with 6 inches of extra fabric around the edges to pull around the headboard.
Lay the fabric for the back panel on the ground, with the foam on top of the fabric. Place the plywood back panel on the foam. Pull the bottom edge of the fabric to the back and staple it in place at each corner. Work slowly from the bottom and up the sides, pulling the fabric to the back and stapling it in place.
Check the front of the back panel as you go to make sure the fabric is smooth across the foam. An assistant can hold the panel upright while you pull and staple, until the material is taut around all sections.
Lay the back panel on the ground. Position the left wing in place with a layer of fabric and foam in place but not secured yet. Mount the wing to the back panel with 2-inch screws.
Work the fabric around the wing front, pulling it all the way to the back edge. Staple the fabric in place on the edge. Trim all excess fabric. Repeat this process for the right wing.