You'll need some paper, double sided medium to heavy weight patterned paper works best. You could certainly do it with card stock as well. You also need a scoring tool, a hot glue gun (very important), and an extra scrap of paper. I used an edge punch as well for added interest.
Determine the diameter of the finished flower you desire. You need to cut a strip of paper 12 inches in length and half the width of your finished flower. I wanted a 2 inch flower, so I cut a 1 inch strip. I also punched one of the long edges of my strip with a fancy border punch for added interest in my finished flower.
Next you need to score your strip at 1/4 inch intervals all along the length of the strip. Since my strip was already punched in scallops at 1/4 inch intervals, I simply scored between the scallops. Easy peasy!
Then pleat along the scored lines and you should then end up with an accordian strip like this.
Next, plug in your glue gun and wait for it to get nice and hot. Punch or hand cut a circle slightly smaller than your finished flower from scrap paper. Fold your strip around so the narrow ends meet with the patterned edge facing out. Hot glue these edges together, creating a circle.