I am making a 50% lard, 50% coconut soap with 3% lye discount as my laundry soap base. I do CPOP -- pour the batter into a mold at medium trace and heat it in the oven at 170 degrees for about 1 hour. So far, this has worked well for me. I do not scent the soap at all when I make it.
I use my food processor to grate the soap one or two days after its made. To the grated soap, I add equal amounts by weight of washing soda, baking soda, and borax. Working in batches, I process the mix until the soap is a fine powder. I found out the hard way that I can't make soap powder just on its own -- the added powders keep the soap cooler and drier while I process it. I end up with a dry laundry soap mix that is very white and has a mild "soap" smell.
Although the basic mix smells fine to me, I have been adding a tiny tish of EOs to the dry mix while the food processor is running. I don't care for a lot of scent -- maybe 10 drops per 1000 grams of finished mix. The scent does not carry over into the clean laundry; I really want just enough to give the soap mix a pleasant whiff of scent when I open its container. I used rosemary-lavender in my first batch and lemon-sweet orange in the second.
If you wanted to scent the laundry, I think I would take jcandleattic's advice. Why scent the laundry water -- most of it is going to go down the drain? Makes a lot of sense to put the scent in the dryer.
--DeeAnna