Put the slate in a container where you can maintain the temperature. I Use a gallon jar in a ten gallon tank. The air should be strong enough to get a good circulation in the container, not necessary that it touch the eggs.
Use anti fungus, Meth. blue, Jungle Fungus Clear, or Hydrogen Peroxide. When they hatch (day 3) turn down the air so it doesn't blow them around and remove the anti-fungal.
Change water every day with same temp water. When they go free swimming (day 9 at 78F.) start feeding newly hatched baby brine shrimp, no other food will do.