Shown here is fabric marked with 8 triangles ready to cut. If I have two layers of fabric I will end up with 16 triangles. I can also add two more layers and end up with 32. (Don't cut more than what you need for the block you are sewing at the time).
Rotary Cutter and metal ruler used to cut through the 4 layers of fabric. I use my metal ruler as a guide for my rotary cutter. Follow the lines marked on your fabric exactly. Make sure your ruler does not slide during the cutting. 
You can cut your fabric with scissors. If you do this don't do more than two layers of fabric as the fabric will slide. And be careful that the two layers are not sliding away from each other as you cut.
