If you want to make this step easier for yourself, you may want to use special comic book paper.
Nowadays it‘s quite easy to find via the internet and it‘s fairly affordable.

The advantages of this paper are:
1) the pre-printed guidelines and rulers make it much easier and quicker to draw panels. The bleed and trim areas are marked.
2) the paper is of high quality so you can erase often without damaging it and the ink won‘t bleed.

And no, I don‘t get paid by Deleter for saying this.
Really... XD