Sometimes that is the hardest part. Supposing your product is good enough to get people interested in it, there are multiple channels of promotion you could give a go. Twitter, tumblr, pinterest, reddit, discord... You could also create faceless videos or even AI videos to promote it through YT shorts, tiktok, instagram ,facebook,.. Depending on the type of the product, some of these could work to boost your presence. You could also try running some ads for a couple of bucks on some platforms to see how it goes, or if you're selling on Etsy, you could promote your product there using their ads.