You can use matches or one of the little Bar B Que lighters. I find wooden matches work just fine. You will want to just pounce it lightly along the edges rather quickly. The edges will melt and curl slightly. If you don't do it quickly it will be to much heat and will melt into a little ball. You might make a few extra to practice on first.
You will then stack together the graduating circles or petals and with needle and thread coming up in the center from the bottom stitch them together. You can then add a button for the centers or you can use pearls, beads or jewels etc. Next stitch or glue your leaves on for a fun flower
A pic of the finished flowers. You can make them fuller or not by the amount of layers you use.