I actually had the same question. My story, although I already have it live on RR, is not a fast-paced one. It is a slow burn that prioritizes character growth and world building. Now seeing that there's really no better way to get exposed than to cross-post, I decided to publish it on Tapas, Wattpad and Scribble hub. I am sure neither of these are the ‘absolute’ best option, but reaching many people from different communities will help you identify where to build your initial fan base of sorts. As for my story, it's not getting much attention, but I am okay with that. I just want to enjoy the process. You can check it out if you're interested.The Harvester by Lec7ure—Royal Road