It took them about an hour and a half. I happen to have some days with triple math periods so it works. Becuase it includes an introduction to the theorem, you could split it easily into two days: one for intro, and one for the breakout.
Students can work as singles or pairs for me but that is totally up to you. I find that having a collaborator helps them think out loud.
Once you make a couple, it does get faster. All depends on how much complexity and story you want to create. I can make most in about 2 hours or less now. My very first one took about 6 hours as I was learning new tools myself along the way. Now I know the tools so just need to come up with the scenario. Hardest part is thinking about where they will run into trouble. Never occurred to me that they would not have played Clue before!