Paint all sides of the bookshelf your desired color.
Lay bookshelf on flat even surface (open side face down.)
Measure the length and depth of the back side of the bookshelf (normally the side that touches the wall.)
Cut plywood to size matching the bookshelf measurements.
Cut cushion foam to same size as the plywood.
Generously spray plywood and cushion foam with spray adhesive.
Attach foam to plywood by pressing down firmly, ensuring adhesive side of foam meets the plywood in all areas.
Check to make sure the the foam is flush to the plywood edges, and not hanging over the wood.
Take batting and wrap the foam cushion & plywood, allowing enough batting to tuck under the plywood on all sides.
Staple batting to plywood on bottom side of wood (the side opposite the foam cushion.) Be sure to tightly secure the corners and all sides.
Take fabric and repeat staple process, securing the fabric with a staple gun to the underside of the plywood.*TIP: Start from the middle of the plywood and always work opposite side to opposite side. This will help to make sure your pattern/fabric stays even and that your material stays taught.
Set fabric wrapped plywood on backside of bookshelf & decorate with pillows.