That is the simplest method. I grew up with a hot-air wood furnace in the basement, and we just stuck a giant galvanized pan on top at the start of the ducting

That is the simplest method. I grew up with a hot-air wood furnace in the basement, and we just stuck a giant galvanized pan on top at the start of the ducting. About once a week I'd have to fill it back up. Man, I miss wood heat.