A landing page is just a page on your blog that you don’t post in the regular blog section. In this case, however, it might be a really big piece of long form content either about the affiliate product or, better yet, one that just mentions the product as a small but integral part of the whole article. For example, your affiliate product might be a great yoga mat and your article might be a complete beginner’s guide to yoga.
Sometimes I think we just need permission to do the things we love without having to make a living at it. So I'm giving you permission. I'm telling you it's fine for you to have a blog that gives you an outlet for your creativity, allows you to talk about things that are important to you and lets you stay connected to friends and family. You don't have to try to monetize your joy.