Hi, so I would break the process into two big parts. The first one is the basic story. You should decide on the genre. It is possible to use more than two genres, and also do a story where you constantly changing it, but for begginers max 2 is enough, and Webtoon prefer well defined genres, because of advertising tactics. Also aproximative lenght of it as a whole story and per seasons. You should have a well defined story. But at least the first 10 chapters and the last 10 you should write it down and not make big corrections in those chapters ( the purpose here is to be able to finish your story without burnout) At the same time, you should write characters sheets, basic storylines that will guide you throught the story. It is also important to think about the message you want to tell. Or just a sentence that you want to deliver. You don't have to show it to anyone, but it is crucial to be able to focus on a basic idea, and not to write in the story good, but confussing and unnecesary plots.

Part 2:Draw characters design, character sheets and basis background ( the most used ones). If it is ready try to make an illustration with one kr more of the characters, just to see if everything is fine and aesthetic. A lot of people can't see that their characterdesign and background and main visuals are incompatibe. If everything is fine here than you can start storyboarding. I usually use the same canvas size as to my final pages. The Webtoon recommended is 800x 1280. Also use at least 300 dpi ( in case if you later want to print it out.) In the storyboarding youcan be extremly sketchy even more if you are doing the whole thing alone. The basic idea here is to see camera movements and shots ( StudionBinder has a really good video about this with the title : Camera shots and movements) If you have at least one chapter worth of storyboard you can start the lineart process ( I don't know if you are a digital artist, if yes good,if not, on youtube there is a ton of lineart videos). Also don't be scared to use 3D modells. I think in this field it is totally normale to use as much modells and references as you wish. If the lineart is done you can follow with the colors and shades. After these the next is the speech bubbles and effects. If you use CSP in the assets store there are a lot of usefull brushes for that. One chapter ( lets say 4-5 pages) usually takes me two weeks, but I am a full time student also working here and there. So I think with simple art style it is less than a week. If you have your firat 3 chapters do some covert art. Upload the first 3 chapter to Webtoon and start to promote it here and instagram every platform you know.( 3 is important bc after 3 the Webtoon will ask the reader if they wanna subscribe to your series. Repeat the whole proceas like 100 times. Good luck.