Make sure your design window is a little bit smaller than your iris template. My heart window is about 4 1/2-inches across.
You can simply use a pair of scissors to cut out your design window. I found that my Cricut Personal Electronic Cutter was the perfect tool for cutting many simple shapes. I used the Cricut Designer's Calendar Cartridge (compare prices) which offered this heart design and many other basic and fun shapes.
You will also want to trim down your cardstock to whatever size you want your finished design to be.
Next, we will cut our strips of paper/fabric...