Glue on any papers or information that you want to include on your poster with regular glue to a cardboard poster. Leave a few corners and edges unglued to mimic a bulletin board.
Press pushpins into the cardboard poster so that they appear to be holding the papers in place.
Hot-glue and pin on 3-D items to your poster board, enriching your display. For example, if you are making a poster about fishing, pin on fishing net. For a poster about Renaissance clothing, hot glue on samples of fabric that mimic the time period and stick a pin through them to maintain the bulletin board look.
Trace the "footprint" of your card stock gift box in pencil on a poster board.
Cut out the traced rectangular shape on your poster board with a utility knife, creating a hole.
Lay the opening of the gift box flush against the poster board. Glue the flaps to the poster board around the hole to secure it.
Place items on your poster shelf.