For quite a while now, I have made my own laundry detergent. I have been fine-tuning the recipe, and wanted to share my new, improved process.
Rather than grate the soap, I have found that if you turn it into a fine powder, it dissolves, mixes, and cleans much better. To do this, start with 1/2 bar of Ivory soap.
Unwrap it and place it into a microwave-safe pie plate or casserole dish (you want something wide).
Place it into a microwave and set the timer for 1 1/2 minutes. Watch it closely while the microwave is on - the soap will grow and expand, much like volcanic lava. When it stops growing, stop the microwave (mine usually goes for a little more than a minute).
Remove the soap from the microwave and let it cool. Once cooled, you'll be able to pull off pieces and crumble it into a fine powder, which you'll be able to easily mix with your Borax and washing soda.
It's also a fun project for kids - my daughter loves to watch the soap while it's in the microwave, and she helps crumble it afterward. Just don't let your kids inhale the fine powder, keep it down near waist level while working with it.