Make your own lye at home, Store bought is Sodium Hydroxide, and what you make at home is Potassium Hydroxide.
Really not much of a difference for soap making purposes.
Couple of plastic buckets, some hardwood ash, and some water.
Drill small holes in bucket #1 lots of small holes, some folks use straw to keep the ash from going through the holes, I prefer cheese cloth or a fine filter paper.
Put perforated bucket with filter and hardwood ash over bucket #2 and pour water over ash, use enough water so it percolates through the ash and drips into bucket #2.
What you have now is a dilute solution of lye water, pour the dilute solution through the ashes about 3 or 4 times to increase the strength of the solution.
I test the strength with a pH meter; but my Mother just used a raw egg, if the egg sinks it’s to weak, if the egg floats high it’s to strong, if the egg floats at the surface it’s just right.
I prefer the pH meter for better control.
If you want it really strong just keep pouring the solution through the ash or toss the wet ash, put in a new filter and fresh ash and keep pouring until it’s like syrup.
Use plastic containers to make it and to store it, the stuff will eat metal worse than salt water.
DON’T USE ANY GALVANIZED METAL.
Mom told me to use rain water because it was the best for making lye (probably because of very little mineral content), I just use my well water (pretty soft any way), but I guess you could use distilled water in place of rain water.
I still remember my aunt making soap clear up into the 1960s. She said she could not stand to see the cooking lard go to waste. she was from the high plains dust bowl era where life was hard and nothing went to waste.