That's what I do, too. I turn my oven on for only 3 minutes (I time it), and then I turn it off . Then I put my soap in it for the night. I used to pre-warm my oven until my oven's thermostat read 120F before turning it off (which was a pre-warm of 5 minutes), but lately I've been doing only a 3 minute pre-warm before tuning it off, which reads as 105F to 110F on my oven's thermostat.my normal technique is to preheat the oven on "warm" a few minutes, then turn it off, put the soap in, and put/leave the oven light on until the soap is firm enough to cut. It's usually still warm at that time).