Unfortunately, time and patience is required. Some SAs took me a good 4-6 hours to make. You can watch the process in this video with my most recent SA that I made: https://youtu.be/M_vJ-Kvpi00
Generally I start off with the base, and set the most prominent shapes first. I decide which shapes work best by taking time to carefully look at what tools I have to work with and glancing at the reference material. I duplicate the base pieces, resize them, and set them on the top layers, and add colour. I pay careful attention to how I have things layered since I may still want the line effects. Then for the majority of the process, I work on the finer details, like making eyes, hair, and other details. Of course, this would work best for complex works. My simplest works usually were ponies (MLPFiM), since they were mostly just a bunch of circles anyways. Depending on what you're doing, it could take anywhere from 30 minutes to 6 hours to make a detailed Symbol Art. Just note there is a limit to how many pieces you can place (225).