This is a project I've wanted to do for a long time. You can do it too! There are only four steps, but with drying time, it might take a couple days total.
1. Find and prime a canvas (Let it dry completely)
2. Cover with color (Let it dry completely)
3. Add pattern and texture (Let it dry completely)
4. Use a thin sharpie or marker of your choice to add doodles and drawings.
I found a couple of wall hangings in the clearance section of a home decor shop. They were slightly damaged, which means I got them for $2.50 each. (You could also check thrift shops for cheap large canvases.) The art was totally not my style, so I was happy to cover it with two coats of white paint.
here and Alisa Burke, who is constantly doing art with her two year old, for example, the one in her office tour here.