I've read you can just use pantyhose. Stretch it over the end of the washer outflow pipe, use a zip-tie to secure it, and then put the outflow pipe back into the pipe leading to the septic.
I actually let the washing machine water head right out to the septic tank. I use biodegradable detergents to try to keep the tank enzymes balanced. We pump it out every two or three years and no problems yet.