The absolute easiest way to make a satirical website is to copy your target’s site directly. Luckily, this is easy to do! You may need someone with some web experience to help, but this way you don’t need to start from scratch.
You’ll need to start by purchasing and hosting a domain, preferably one that looks a lot like your target’s real domain name.
Then can choose just to copy one page of your target’s website and link to your fake page. Or, you can copy the whole site and make changes to your favorite pages.
To copy just one page, use your browser's "Save As" feature and select "complete HTML." This is the easiest—saves the file but also saves all the links pointing to the original site. Edit the page and upload to your domain. (Also upload an index.html that resolves either to the target website or to your special release page.) Optionally, for a site that’s extremely simple (one page), this can be enough.
To copy the whole site, you'll need something like PageSucker or WebDevil to suck down whole site. Then you'll want to prune the site down to maybe 4-5 pages, and then edit those pages. This can be a lot of work, to make it work right.
As for the risks: your target may send you a meaningless legal threat known as a cease-and-desist letter, saying that they might sue you—which they might, but almost certainly won't, especially if your content does something subtly satirical—so that someone reading closely might understand that it’s fake.
For good measure, in the event of such a threat you can get pro bono legal help to respond to your target or otherwise advise you. The worst that can happen, probably, is that you’ll decide to take it down; this is very rarely necessary. (Note: we're not speaking as lawyers here.)