Wash and dry the rocks completely before painting. Any grit or moisture prevents paint from bonding. Apply one coat of acrylic paint all over the rock in a chosen monster colour and leave it to dry for 30 minutes. Apply a second coat for solid coverage and dry again, about 20 minutes. The painted surface should look even with no rock texture showing through.

Once the base coat is dry, glue two googly eyes onto the upper half of the rock and press a small pom-pom between or below them as a nose. Hold each piece for 20 seconds until the glue grips.

Use a black paint pen or fine marker to add a mouth: jagged teeth, a row of dots, a wavy smile. Add eyebrows, small horns drawn in lines above the eyes, or spots of contrasting colour for extra character. A white paint pen can add a highlight dot to each googly eye to make them look more alive.

Leave the finished face to dry for 15 minutes. An adult then takes the rocks outside and applies a light coat of clear acrylic varnish spray. This step seals everything and stops the googly eyes peeling off later. Allow the varnish to dry for at least 20 minutes before handling.