|I use a rotary mat and rotary cutter to cut my knit fabric pieces. This is typically a quilter's accessory, but works great for me with my clothing projects! With the smooth, sharp, and straight cut I get by using a rotary cutter, I can even get away without hemming some of my knit pieces using this technique.
I use the smooth decoration rocks that people use on the decorative plates that go around candles for my weights. I also have a smaller rotary cutter for the corners, or just use a pair of scissors for that small portion. Works great!