Unmolded my soap today. The good batch is looking pretty good (although I probably should have put some effort into removing air bubbles). The dodgy batch has been melted down and poured into new molds, hopefully it has been saved.
It's not very complicated to make a basic soap, most difficulties come in when you are trying to add colours and fragrances. I mix it under the rangehood to deal with any fumes from the caustic soda. It's basically a process of warming up the oil to around 54 degrees, mixing the caustic soda with water and waiting for it to cool to 54 degrees, then when they are both at the same temperature mix them together until it starts to thicken - I use an old slender blender so don't need to have strong arms, and it mixes in a couple of minutes. Then you just pour it into the moulds and wait a bit. You can use something like a milk carton lined with baking paper, then in a day or two cut it into slices and leave it to dry for around 6 weeks to fully harden.
These batches are made with beef fat which I collected off a very fatty batch of soup bones I made stock with a while ago, so they should also count as quite frugal!