I am also trying to learn Affinity Designer. I came across a YouTube video by Serif Affinity Designer that shows how to create a Mandala using any of the drawing tools: the Pen, Pencil, or Vector Brush Tools.
She demonstrated it using the Pen Tool, Symbols, etc. It may sound complicated, but it’s not, although it isn't so well explained like Ally from Affinity Revolution.
By slowing down the video speed, turning on the subtitles, and going back and forth, I could achieve something—not there yet, but at least something.
However, there is a long way ahead of me.
Edit: Now I noticed that the guidelines are showing... See, not there yet! 😄