In simple terms, a cover inset is simply an indentation or window in a book cover into which an object is placed.
Here are some of the simple steps and some ideas for making your own book cover insets.
In this example, a polymer clay tile of an elephant will be inset into the book's cover. Before any cover stock is adhered to the book board, the tile is positioned and its outside edges traced onto the cover.
I generally add 1/16" of an inch on two adjoining edges to the cutout, allowing a 1/32" border space around the inset item. This allows for the space taken up by the cover stock inside the cutout and permits a tight fit.
Using a razor knife, the opening is cut out, but only cutting into a depth of about 1/3 to 1/2 the thickness of the board. This takes some practice, but it's easier to estimate by placing your blade next to the edge of the board to see how deep the blade should go to only cut partially into the board.
Using an awl, layers of board board are picked away and removed from the cutout section. The inside of the cutout is smoothed with a wood chisel and a small bit of sandpaper to get it flat all the way across the bottom of the cutout.
The depth of the cutout is generally determined by the thickness of the item being inset. In the example on the right, the elephant icon tile was thicker than the Scrabble tiles, requiring it to be inset slightly deeper than the letter tiles.
After the cover stock is glued to the bookboard, it is pushed into the inset with a bonefolder to allow the inset item to be attached. Cutting an "X" in the middle of the coverstock makes it easier to push it into the cutout.
As shown in the example, the autograph book was further embellished with beads strung around the binding posts.
A simple way to make an inset object is to wrap a cut microscope slide with adhesive copper tape, holding a home-printed title in place behind the glass.
In the examples to the right, the tape was treated to Liver of Sulfur to give it an interesting patina.
As in the earlier example, the bookboard is cut out to the desired size and depth, then smoothed with sandpaper and a wood chisel.
Taking a little extra time to smooth out the cutout section really makes a big difference later on. This permits the inset item to rest more evenly inside the cutout section, making it more secure.
Some additional ideas for insets include:
Cut a window all the way through the cover and glue a thinner sheet of chipboard behind it to create an indentation in the cover. It is advised to start with thinner book board since you'll be laminating an additional layer to create the inset.
Use a Dremel power tool like a miniature wood router to remove the board from the cutout section. This works pretty well, but a great deal of airborne bits of book board results. It can be pretty messy and fills the air with paper fiber.
Any sort of item can be placed within the inset, but it is advised that it has a flat back side to make gluing easier and more secure.
Consider stitching or using other ways (rivets, brads, twisted wire) to hold the inset item in place. If desired, the holders are seen as part of the cover's design aesthetic.