My process starts once again with sketching - I use the Procreate app on my iPad and start from the center of the canvas with the main element. From there I build further the artwork and expand it with more elements on each side.
I make sure I fill up all blank spaces proportionally, and when I am happy, I start defining the design with crisp lines. The next step is of course deciding on the color palette and adding the colors. Depending on the project and background those could be different. When it comes to me deciding, I usually use websites such as coolors.co.
The final process is what I call "technical" - this is transferring the artwork to Adobe Illustrator and vectorizing it. This way I make sure it is scalable and with crisp lines. Making the pattern from there is straightforward - I just define it and insert it into the swatches.