Draw thick straight lines from the edge of a sheet inwards, about three centimetres apart, and let your child cut along them to make a fringe.
When straight lines are comfortable, draw wavy ones. Curves need the paper to turn rather than the scissors.
Stick the fringed pieces together into grass, and the cutting has produced something worth keeping.
Cutting is one of the most demanding fine-motor tasks a preschooler attempts: one hand opens and closes the blades while the other feeds and rotates the paper, each doing something different. That asymmetric coordination underpins handwriting.