This is a mono print on a paper collage (with a little spray painting too). I'm going to show you how I made the tree shape.
You need a sheet of plexiglas and some masking tape. I used painters tape here. With strips of tape, I created a tree shape. I didn't over think it and I created it quickly.
Then, using a brayer, I rolled the paint over the tape and onto the plexiglas. I used Golden Open Acrylics (because they are slower to dry) but you can use regular acrylics and work quickly (or add extender).
Cover the whole thing with paint, and better yet, blend a couple of shades of color.
Next, peel the tape off the plexiglas. It's easy as it comes off in one big piece. Shown is the plexiglas, with tape removed. The paint is still wet.
Place a piece of paper on top of the painted plexiglas, and brayer over the back to create a print.
Lift off the paper and voila! I did this sample on plain white paper, but as I showed you, you could do it on a collage, or previously painted paper.