Great question — answering as the UphillTech team:
I think this is going to be a bad idea; you'll go from ideal couscous texture (fluffy and light) to mush. I have an article (on my blog) about how to make fluffy couscous . The crux is simply to put it, with the appropriate amount boiling water, in a wide, shallow vessel and cover it for 5 minutes. You can even set that up ahead of time, and when you are ready to serve the food from your crockpot, just add the boiling water from a teakettle and you'll be good to go.
Full answer by Michael Natkin: https://cooking.stackexchange.com/a/6791 (CC BY-SA 3.0).
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