Why are you making your own laundry soap? If you are doing it strictly to save money, then most of the above suggestions would be fine.
But if you're looking to control the kind of substances you bring in your home and subject your family to --
most bar soaps that are sold in the typical supermarket or walmart store are full of detergents and sythetic fragrances - petroleum derived. There isn't much of a health benefit if you go that route, IMO.
An aside: when I was a teen, I worked in a fancy boutique one summer. We sold a very expensive line of health and beauty products. One day I came in and the boss was in a panic pulling products off the shelf
- the manufuacturer was recalling a batch of soaps and lotions.
The items had made it out of the plant before the "cover" fragrances were
added.
Out of curiousity, I started opening bottles and sniffing. Talk about an eye opening experience. Those products stink to high heaven because they HAVE to cover up the petro-chemical smell. They smell like a refinery!
For me, it was a fortunate learning experience. I swore from then on that I would always take the trouble to find real soap, and naturally-derived products.
It wasn't long after that when I noticed I couldn't stand the stink from just walking down the soap aisle in the market... instant headache. Once I started avoiding that junk, my sense of smell completely changed - for the better.
OK, done.