Doctor Who Fez
Materials: 1/8 to ¼ a yard of felt, string (or a purchased tassel), thread, thin cardboard or thin craft foam, scotch tape, duct tape, fabric scissors, pen, straight pins, sewing machine, glue gun, paper for printing the pattern http://tallystreasury.com/wp-content/uploads/2011/05/fez-pattern.pdf
Step 1: Start by printing out the fez pattern onto plain paper and cutting it out.
Step 2: Pin the pattern onto the felt and cut out all of your pieces.
Step 3: Fold piece B (The brim of the hat) in half, pin and sew together. The outside of the piece will become the inside of the fez.
Step 4: Now take piece A (the circular piece) and set it on the inside of piece B. Pin all the way around.
Step 5: Sew all the way around the circle, on the inside. Make sure you are sewing with piece A face down, laying against the sewing machine.
Step 6: Cut small slits all the way around the top part of the circle, but not cutting the thread. Flip inside out.
Step 7: Take the pattern pieces from before and cut along the dashed line-the circle will be a little smaller and the long rectangle will be narrower.
Step 8: Trace the new pattern pieces onto your cardboard or craft foam and cut out.
Step 9: Glue the circle of cardboard to the inside of your fez. Tape the pieces of your rectangular foam and place in the hat. Cut to fit-you should have about an inch more fabric than foam.
Step 10: Glue along the bottom exposed edge of the felt and fold into the fez. Continue all along the bottom edge. Let dry.
Step 11: Flip hat over and attach the tassel.
For full tutorial with pictures, see this.