Begin by creating the shapes of your monsters.
Squares, circles, ovals, triangles, diamonds, pentagons, rectangles. All you need to do is draw a shape with a black marker on a sheet of white cardstock and make a set of simple arms and legs. I found that 2 monsters work well on one sheet, but you could make a single large monster, too.
Now, dip a fork in a squirt of paint and begin making the monster.
Use the tines of the fork to make a furry look. Let the paint dry.
Draw a monster mouth on another sheet of white cardstock. Make the lines thick enough to cut out.
Glue a googly eye in place. Large eyes, multiple smaller eyes. Whatever your monster has going on. And glue on the monster mouth.