You will need the following ingredients to make your own laundry detergent:
1/2 cup of borax
1/2 cup of washing soda(not baking soda)
1/3 bar of fels naptha or other bar soap
You can find these ingredients at your regular grocery store in the laundry detergent isle or Walmart. Some people have trouble finding the Arm and Hammer Washing Soda but I know you can find it online or even on Ebay. You have to factor in shipping so it may cost a little more if you have to go that route.
The first thing you want to do is grate the whole bar of soap and divide it into 3rds. That way when you want to make it again you already have your soap divided up.
Second step would be to add 1/3 of the fels naptha soap with 6 cups of water and heat on stove until the soap is all melted. While your preparing for step 3 heat 4 cups of water in microwave for 3 minutes. Add 1/2 cup of washing soda and 1/2 cup of borax and stir until dissolved. Take off stove. Add your 4 cups of hot water in your bucket, now add your soap mixture. Then add another gallon plus 6 cups of regular water and stir. Stir very well then let sit for 24 hours and it will turn into a gel-like substance. Depending on whether you have a front loader or regular washer you will use between 1/3 cup and a 1/2 a cup per load. This process takes no longer than 15 minutes to accomplish and will come out looking pale yellow and be like a watery gel-like substance.