All you need is an Amazon Affiliates account, a subreddit in a specific niche that allows affiliate links, and some good deals from Amazon. The key is to find a subreddit with a warm audience who are already interested in buying something. I then recommend finding lightning deals or other steep discounts on Amazon that are loosely related to your niche and posting them with a descriptive title on the subreddit. The goal is to get your affiliate cookie on as many devices as possible, because you get commission for anything they buy within 24 hours of clicking on your link. By doing this, I have generated over $7,000 in affiliate Amazon sales in the last week, with an average of about 3% commission.
The goal is not to get people to buy what you link, but to get as many clicks as possible. Therefore, it is important to find deals that make people click, not necessarily buy. Additionally, it is recommended to add some personal touch to the post by adding some text like "thought this could be useful to you guys" or other similar text. It is also advised to be somewhat active in the subreddit prior to the first post, so that the mods are less likely to ban you for spamming.
I suggest taking it a step further by purchasing upvotes and engaging on the post with alt accounts to make it seem well received. I also recommend finding someone who runs an affiliate website that scrapes deals in your niche automatically. All you have to do is go to that person's site, grab your own affiliate link to those products, and post them on the subreddit.
It is important to note that you only get your commission once the item is shipped, so half of the commission is still not accounted for. Overall, this method is simple, low effort, and highly effective, making it a great way to earn some extra income on the side.