I've never tried this but without a seafood rack or frog mat you could try parchment paper for baking. Most grocery stores carry that. My wife bakes with that at 300 degrees so that or spraying the rack with "Pam" or as we use olive oil spray helps too. You will learn a lot from this group, I sure have and I've had my smoker less than 2 months, a wealth of information here on this forum! Have fun with the salmon, it'll be yummy good!!
I found this quote on SmokinKings forum about parchment paper:
"I use parchment paper all the time when I smoke meatloaf and I've used it with skinned fillets of fish too.
The smoke goes right through the parchment so I get the same smoke ring on the bottom as top and sides, and the paper comes off cleanly when you are done. I think it could be a good answer for you."
And Chrissy, if you do use parchment paper for the salmon smoke, be sure and post your results here, it would be good information to have ;-)
Carl