Using store bought post it or sticky notes.... measure and cut 2 sheets of paper to fit the front, end panel and back of the post it notes. (just slightly bigger to allow for the curve and corners of the cardboard)

Then cut a front panel, back panel the size of post it notes... using medium to heavy cardboard.

For the end size the small piece and cut a cardboard... but cut it slightly smaller .. you will be leaving a spacer between the sides of end panel.... see photo below.

Above is a photo of the cardboards as they will be glued to both sides of the 2 papers. (If you cut a slight bit larger you can always cut the ends after gluing and getting the correct size.)

When gluing the 2nd paper to cardboard be sure to add extra glue in the valley fold space between and using your scoring tool to push the papers firmly between the folds.

The extra space allows for your base to fold easier.

Attach the back of the post it notes onto full back of the cover.

**** to attach the pens on a ribbon tie the end of ribbon to the pen  ***** leave extra length of ribbon for the pen to reach around and write to bottom of post it note. Glue the other end of pen ribbon onto the end panel of the base... glue full end panel and glue to end of base. Hold firmly until it sets. 

Now tie another ribbon around the base and pen and tie a bow.

These 2 are decorated for Valentines Day.... but like I mentioned.. you can decorate for any occasion.