I found some good resources, thanks.
I think it will use a good size piece of drift wood and have it going diagonal to up the slope and poke out of the water as it hits the island I made with the substrate then attach the moss to the top of it, being that flame moss likes to grow vertically.
I found this link Freshwater Aquarium Set-up: Adding Driftwood to Your Aquarium
which says I should boil the driftwood before using it, should I do this?
Also what kind of wood do you recommend?

Thanks again for all of your advice I am putting it to good use, I want Casper to grow into a happy and healthy bullfrog!