Today, a search for "slime" on YouTube yields more than 20 million results, but at the time, content like Garcia's was rare, and she got in on the ground floor of the sticky business.
"My first check from YouTube was only like $50, but then it kept getting bigger," says Garcia. "The paycheck that was like super crazy to me was when I got a $10,000 check. That was when I felt like I made it."
Garcia received that check less than a year after uploading her first video.
YouTube declined to comment on Garcia's earnings, but Danny Fratella of Social Blade, a data company that tracks estimated earnings and future projections of YouTube stars, estimated that Garcia likely earns anywhere from $80,000 to $160,000 a month on ad revenue alone.
"She has over 960 million total views on her channel, which have likely paid out several million dollars in ad revenue over the life of her channel thus far," Fratella told CNBC Make It via email.
Garcia has also secured partnerships with brands like Coca-Cola, Audible and Maltesers, and completed a 14-city meet and greet tour last summer. In May of 2017 she published a book, "Karina Garcia DIY Slime," and in October she launched a product line, Craft City, which includes a make-your-own slime kit sold exclusively at Target.
She says that between ad revenue, partnerships, her book, product line, and events, her business earns about $2 million a year.
One of Garcia's most popular videos to date has more than 23 million views. In it, she demonstrates how to make a stress ball out of 100 pounds of slime. Its popularity is a testament to the internet's growing fascination with slime. More than six million Instagram posts bear the #slime hashtag, and on Google's 2017 top trends list, "How to make slime" was the task most searched.