My suggestion would be start with modifying one of the existing presets. Take “Molten Floor” and just change the damage amount. Try out “Fire Dome” and see if you can make the circle close in faster.

The key here is start small, and ask questions often!

One creator had the idea of just switching to the hero that you want to use the ability on:

I understand this isn’t exactly what you’re looking for, but there are lots of ways to do things in the Workshop! Some of them will take time to find out and share with each other, so let’s all help each other out