Paints with liquid watercolor, in the theme #herfst .
With (once made by myself) templates of autumn leaves, these drawn on A3 sheets.
Then lines criss-crossed.
And then it's a question of filling in the boxes.
Source idea: Pinterest.
Own elaboration. Bottom result is from my son. In the upper part, the autumn leaves were no longer clearly visible. That's why I checked the edges with red marker. Unfortunately, the paper tore a little, because it was still damp.