I've just set my culture up. I put 1/4 of the starter in a 1 quart mason jar with the cream etc. (because I'm starting with a low dose).
I put the mason jar on a folded tea towel inside my kitchenaid mixer bowl. [The mason jar is only half-full, but the water level has to be high for the heater to work. The mason jar tips because it's too lightweight.......unless I raise it up.]
I hung the aquarium heater off the kitchenaid bowl and plugged it in. When it's on, it throws a yellow light.
I added 80 degree water to the kitchenaid bowl up to the line on the thermometer, and then adjusted the temperature knob until it went off. I'm now watching the temperature and fine-tuning the knob, as the starter mixture warms up from refrigerator temperature.
The instructions say nothing about covering it, but I've folded a piece of plastic wrap up, and placed it lightly on top of the mason jar.
5 days from now I'll take my first mini-dose and put the rest in the fridge.
ADD: The starter measures 1-1/3 cups, so I stirred it well and used 1/3 cup. If you do this, be very careful re-closing the jar. I almost dumped it all out on the counter.
Also, avoid metal completely.