Measure the spot where you want your message board to hang. The wall message board I made was 20" x 24" and the locker message board was 6" x 9". Use a sharp knife to cut your styrofoam to the desired size. Cut a piece of fabric so it is approximately 3-inches larger, on all sides, than your styrofoam piece.
Lay your piece of fabric face down on a hard surface. Lay the styrofoam, centered, on top of the material. Glue the fabric onto one of the long edges of the styrofoam, let cool. Glue the material onto the opposite side, pulling the fabric tight so it is smooth on the front side.
Fold up and glue the two shorter ends like you are wrapping a gift - fold down the top flap, fold in both sides, and then fold up the bottom. If you like, you can then cover the back with another piece of fabric or felt to cover the raw ends; however, this might make it harder to hang.
Once the fabric is glued in place you can add the ribbon as you please! While the ribbon is not mandatory, it is functional! Messages and photos can simply be tucked between the message board and ribbon to hold them in place without leaving holes from tacks.
The best technique for larger boards is to make a grid pattern, spacing the ribbon a few inches apart. Put a dab of glue on the ribbons where ever they intersect to hold them down. With smaller boards, you might just want to add the ribbon in the corners. Experiment to find the design right for you!
You can also decorate your message board by gluing on buttons, ribbon rose, etc. To make these items useful you can glue them onto tacks!
For my smaller, locker message board, I covered the entire back with a magnet sheet and it works perfectly. To hang your message boards on a wall, simply place a few nails or screws in place and gently push the board onto them so they poke through the styrofoam.