I used an online program called "Sketchpad" if you'd like to use the web tool I used for the trees. I was overall just messing around with it, but I'm very happy with the result.
I wanted to do a simple pen sketch, where if I mess up it is permanent. The one drawing type robots can't replace. #DOWN WITH THE ROBOTS, ROBOTS SUCK!!!!#
Freehand sketching in ink from a photo reference I found online, to practice conveying that lots-of-stones look without drawing all the stones (photo credit: K. Mitch Hodge). Micron pens + alcohol markers.