How about sowing them on a good seed compost and covering them with a layer of vermiculite. This will help prevent fluctuations in temperature, and help keep the soil moist, and will help prevent damping-off.
Also, put a clear propagator lid on them, or put them in a clear plastic bag, that´ll keep them warm and humid. But give them some air when they germinate, as this will help prevent damping-off.
And keep the soil moist.