Just post the link+description of your custom race or deathmatch. You can find the link on your Social Club page > Share button > Copy Link.
Off road : Wet and Muddy Zancudo
A trip around Lago Zancudo. Don't let the water slow you down!
Planes : Chiliad Up and Down
Dedicated to all the crazy pilots, appoved by Trevor Philips.
Boats : Jumps Shark
Some jumps for your boat; Seashark recommended.