Calculate the needed fabric width and length using this formula: Add the headboard front width + 2x the seam allowance (we used 1/2" seams) + the headboard depth. Ours was 44-1/2" + (2 x 1/2") + 2 = 47-1/2" and we rounded up to 48" wide. The formula for the length is as follows: Add the front headboard height + back headboard height + headboard depth + two hems. Ours was 18-1/2" + 18-1/2" + 2" + 2" + 2" = 43". Now it's time to cut the fabric piece. Ours was 48" x 43". Note: Because we used fabric that was only 45" wide, we chose a pattern that could be rotated 90 degrees and still look good. This let us skip a step of piecing fabric together. (If your headboard is large or your fabric's pattern would not look good rotated 90 degrees, then you can piece your fabric together). Alternatively, you can follow our tailored headboard slipcover method and just add the pocket from this tutorial.
With wrong sides together, sew the left and right side seams of the headboard slipcover using 1/2" seams. We sewed our headboard slipcover first and then added the storage pocket. Depending on the size of your headboard and where you'd like to place your storage pocket, you may choose to add the storage pocket before sewing side seams.
Determine the desired size and placement of your pleated storage pocket. Our finished pocket was roughly 9" at the opening x 11" at its widest point. Cut two rectangles for the front pocket and back pocket. (Ours was 8-1/2" x 11"). Round off the bottom two corners by tracing around a glass or other round object and then cutting the fabric. Cut one piece of fabric for the top pocket facing. Ours was 4-1/2" x 9-1/2". Here's the formal calculating for the top facing: for the height, calculate 4x the desired height. (Ours was 4 x 1", so 4".) To calculate the top facing width, take the pocket's width (ours was 11") and subtract 2" for the pleats + 2x the pocket seam allowance. (We used 1/4" pocket seam allowances, so 1/2" total.) Optional: If your fabric is thin, cut one piece of sew-in interfacing.
Baste the pocket pleats and remove the pins, then slip the raw top edge of the pocket into the long open side of the pocket facing and pin. You'll notice that the pocket won't be totally all the way inside the pocket facing, that's okay! It will actually curve more in the end, which is good.
Pin the storage pocket to the headboard slipcover where you'd like the pocket to go. Optionally, you can highlight the pocket by slipping rick-rack between the pocket and the slipcover. Then sew close to the edge to secure the pocket to the headboard slipcover, remove the pins as you sew.
You may choose to secure the slipcover to the headboard to counter weight in the pocket. Follow package directions to attach a loop (soft) side of Velcro to the back of the slipcover on the wrong side. Place a piece of painter's tape onto the headboard to protect it from the Velcro's adhesive. Place a hook (scratchy) piece of Velcro onto the painter's tape. Wait 24 hours for maximum hold, then attach the Velcro fasteners together (Image 1). Since the slipcover is removable, it's a great, inexpensive way to decorate a kid's room to fit their fancy (Image 2).