We usually prepare it on a three-day weekend, making the stock and first stage of the sauce on Friday, then finishing off and eating on Saturday. For us it's a lot of fun to start preparing it after work on Friday, having a few drinks, listening to music while we chop, drop and stir. The easiest way to make the stock is to buy a few cans of Campbell's chicken broth. Making a stock is one of the simplest of all cooking skills, in large part because it's almost impossible to screw up. The ingredients need to start off in cold water, so their flavors can be gently extracted from them.
Hot water is too much of a shock.
Very few ingredients bland out a dish like celery does. Half a stalk is great. A whole stalk will turn your stock into yellow water. Plus it's easier not having to peel the skin and cry, cry, cry during the process. The reason why you're doing this is to intensify the flavor.