Begin by measuring out the three main pieces and cutting them from your mdf or baltic birch plywood. Mark all pieces before you cut them (a table saw with a special fine blade is preferable for MDF). Ensure you cut outside your measurement lines and allow for the width of the sawblade when you cut. Work in a well ventilated area and avoid breathing in the dust from the MDF. If you wish to insert a window in the back wall of the bookend measure the opening and use a drill bit to create a starting point inside the measurements for each corner, then use a jigsaw to cut out the window area.