Make a heart photo page. Cut a piece of copy paper to 3.5" x 5.5". Fold it lengthwise and cut it into the shape of a heart to make a template. On your computer, size a photograph to approximately 3.5"x 5.5". Print it on a sheet of photo paper, place the template over it and trace around it, then cut the photo into the shape of a heart.
Open the Moleskine sketchbook to the first page (the one that says "In case of loss, please return to…"), and use scissors to carefully cut it from the bottom to the top of the page, leaving a \u00bd" "tab" of paper connected to the binding. (Don't discard this cut-out page, you'll need it later.) You may also need to remove the second page, if they're glued together near the binding. Use the double-sided tape to affix the left edge of the back of your heart-shaped photo to the tab, then trim the tab down so it's less noticeable in the spots where the heart is not attached.