I soaked the plank for about 2 hours. Had the UDS humming at about 300 degrees. Put the potatoes on the bottom rack for an hour. Then placed the wet plank with the salmon on the top rack.
After about 90 minutes the taters were done, so I put the plank on the bottom rack and the taters on top.
I've done the planks on my OTG before, but I really liked the UDS version a lot better.