a whole bunch of these about ten years ago when I was at
a week long artist residency. I had set up a still life and then
divided a half sheet of watercolor paper in random squares
and rectangles with artist tape, trying to vary the shapes
and sizes. Then I painted across the paper focusing in on
different sections of the still life, while trying to think of all
the smaller images as still part of a whole and make the
composition(s) work. Color, design, shapes etc..
It's a workout for your brain and brush!
I've tried this exercise with some of my workshop participants.
It's fun to try..somehow it makes you less concerned with
trying to end up with one "finished" painting.