I wouldn't bring it up, because if he's not cool with it, you don't get your way.
I'm guessing you don't know this guy or else you'd two be comfortable with it. I would just start by lounging around wearing less. When you're hanging around, wear a pair of lounge pants or shorts and go shirtless. Hang out in your underwear. Walk around in your towel. Sleep naked and when you have to get up in the middle of the night to go to the kitchen or whatever, walk around naked. Change with your door open.
After doing this for a while, see if he does it, too. I wouldn't bring it up, but say things like, "Ugh I just got get these pants off, they're killing me." or "This shirt is so uncomfortable" and take it off.
Maybe the best thing to do is to hang out in your underwear, spill something on it, and say "Fuck it," and take it off and just chill nude. Be like, "I hope you don't mind dude...just thought I'd air out a little."
My roommate and I walk around in our underwear, and sometimes nude throughout our apartment. He even answered the door nude one time and didn't realize it...hilarious.
Just get him open to the idea...