So, you don't need a slalom boat to do slalom. All you need is to find races near you and enter them. A slalom boat will enable you to be more competitive yet it's not strictly necessary or even wise to buy a slalom boat until you know if you like it. There are a lot of races where boaters share boats.
Where I learned slalom, once you got to know the other racers you were both welcome and encouraged to practice/race in every boat class you felt comfortable with. Further to that, anyone racing in their creek or even play boat was encouraged. We made classes for short boats, long boats, duckies, and race boats. Some races lump all boats together which makes the competitive nature of mixed boats a bit skewed but no less fun!
On the river, I can abandon who I am and what I've done. However brief it lasts, while on the river I am nothing important and everything insignificant. I am flotsam, and happy to be so.