Hot water heater, cable box top of the fridge (though mine doesn’t get warm enough) I have a heating pad that gets 82 on low and I use that most of the time.
I leave mine in a shot glass until they tail, no matter how long that is and I use filtered tap water. I quit using the paper towel a couple of grows back because I seemed to get the same results just leaving them in the water. If one sinks I re-float it with a spoon. I’m 100% that way. Generally they soak for 24-48 hours and into the soil!
But there are many ways to germinate and they all work!