Start with a piece of 11-1/4" x 3-1/2" DSP.
Score at 5", 6-1/2".
Cut a piece of DSP 1-1/2" x 3-1/2" and score at 1/2" for the flap.
Fold on creases, and attach flap to top/back side of bag.
Cut a square in the front using a square die.
Decorate as desired.