First buy a grocery stand that has metal wired frame with one or two decks. You will need a handkerchief as a soak to cool the vent. A vessel to hold water or salted water (to prevent smelling) for the handkerchief soak. A small box on which to keep the vessel with water to allow elevation for easy soaking.
Most laptops have a vent for hot air to rush out at one of the corners at the back or side.
Keep the laptop on the grocery wire stand and figure out which corner the hot vent is. We will make a water soak with the help of handkerchief folded into pleats or as a flat roll at the hot vent. The analogy is given like a wet cloth hung on a wire to dry. Similarly, keep the handkerchief folded into a long piece of cloth dipped into the water. The kerchief should be hung on the rim of the stand in such a way that it is facing the vent. Take care not to close the vent, by leaving a small air space between the laptop rear and the wet kerchief.
Now your laptop stand and the vent cooler are ready.
Since the outlet hot air vent is being cooled by the wet kerchief soaked in water, the water in the vessel will come down in a day. So take care to refill the water everyday. You may need to place a box to elevate the vessel for better soaking of the handkerchief.
Believe me the hot air vent will cool due to the air flow that carries away the heat though the water that vaporizes from the handkerchief.
And your other inlets of air for the laptop will receive fresh unhindered air from other air inlets at the bottom of the laptop.
I have used a variety of cloths to air cool the vent by soaking and found that different fabrics give different level of air cooling. Cotton fabrics used for making professional blazers work better than mere cotton handkerchiefs. Or put in a simple way, you may try long pieces of unused cloth from a tailor's waste to make the soak. Knitted fabrics with different designs work as better water soaks than simple knitted fabrics.