The shutters are mounted to the face of the bookcase. Choose a pair that's the same height as the bookcase, or add a header board to make up for the difference. The top and base are cut to the width of the bookcase, and extend past the front to cover the edges of the shutter doors and leave a reveal.
You can use the cut list below or download the cut list to build a cabinet from a bookshelf and shutters.
Bookcase. Choose a small bookcase with adjustable shelves. (Ours was 29⅝"W by 11⅝"D by 31⅝"H.) The toekick, if it has one, will be covered by the shutter doors.
Shutters for doors. Choose shutters sized to the height and width of the bookcase. (Ours were by 14¾"W by 29"H.) If the shutters are shorter than the bookcase, add a header board at the top of the bookcase to make up the gap in height. Once installed, the shutters should be flush with the sides of the bookcase, with a gap of about ⅛ inch between them.
1x utility shelving. You'll rip the top and bottom of the cabinet from this board. The length of each piece will equal the width of the bookcase; the width of each piece will equal the depth of the bookcase plus the thickness of the shutters, plus ¼ inch for a reveal. To make sure you have enough material, get a piece that's at least twice as long as the bookcase is wide, and wide enough to cover the depth of the bookcase plus the thickness of the shutters and reveal.
1x3 to create a header, if necessary, and a stop block for attaching the magnetic door catches. Get a piece long enough to span the width of the bookcase, plus several inches for the stop block.
¾-inch trim. Get enough to cover the front and side edges of the top and bottom of the cabinet.