What you need:
Water-currently we all have that.
1 cup Borax- I have seen this everywhere, Safeway, Albertsons, Target- You name it.
1/3 bar Fels Naptha soap (This is the part I would change)
1/2 cup washing soda(a bit harder to find but Fred Meyer has it for sure)
and a 2 gallon or larger bucket.
2 to 4 tbsp of your favorite essential oil (optional)
so here is what you do:
cut up your soap or grate it into a sauce pan with 6 cups of water and heat it until the soap is fully melted. It took a bit longer then I had expected so be patient. Something I am working on. Now add in the washing soda and the borax and stir it all up until dissolved. Remove from heat and add 4 more cups of Hot tap water. pour mixture into your bucket and add a bit less then 1 and a half gallons of water. Add essential oil (I love either lavender or sweet orange.) Stir it all together and let sit over night. It turns into a sort of gel or the sort of slim stuff you see on the Nick Choice Awards (Yes I have kids and watch to much TV.) Most the recipes I found recommend 1/2 cup per load.
I am not completely sold on this recipe. Personally I like to see suds. I know, I know suds don't mean something is clean, but they make me feel clean so next batch I will add 1 hole bar of the fels naptha soap.
It was pretty fun to make and now that I have tried it once the next go around will be a kid and mom activity.
Lastly this soap is way cheaper then buying laundry soap, especially if you are buying the eco laundry soap. The costs works out to be about a third so give it a try and tell me how it goes. You can adjust any of the ingredients you want to. I have heard some people like to double the borax to boost stain removal. I tend to pour a bit of extra borax right into the washer with my laundry soap when washing heavily soiled cloth anyhow.
Good luck and happy washing!!!