Hmm... I think the key word for your game here  is "hyper casual" because it looks like SliceGo only focuses on the slicing mechanic. I think your best bet is to find people who like hyper casual games FOR being hyper casual, not just because they happen to have played a hyper casual game once before. Chances are if they like those games and play a lot of those games, they'll want more of the same. Maybe you can find them by browsing hyper casual related  games, webpages, forums, Twitter accounts/Tweets,  discord rooms, etc. the list goes on. Once you learn to find them, oh man, it gets fun. You can ask them for feedback because they know more about those types of games than random people on the internet and with feedback you can refine your game to suit that kind of audience and maybe even give it a price. Good luck!

To be honest, I don't know either, but I think if you understand the basics of marketing and you're constantly doing whatever you do BUT also improving at it regardless of status results, marketing will get easier and easier because 2 things: 1) Your content will be higher quality and more eye-catching and will hook viewers' interest to the rest of your content, and 2) You're constantly getting more eyeballs with every piece of content you create and people will start talking about it and it just kinda starts going more viral over time. The key is to do what you enjoy, but also provide value to people - that's the ultimate rule, don't focus on numbers so much, focus on the long term fulfillment of what you do and results will come.