An open-ended activity does not need a complicated script. Invite a child to arrange age-appropriate pieces into a place, a pattern or an imaginary character, then let the idea change.
Offer a small starting point
Try a question such as, “Where might this character live?” Avoid deciding what the finished result should look like. Follow the child’s interest and leave time for repetition.
Keep the setup appropriate
Choose materials suitable for the child’s age and abilities. Follow the toy’s age rating, warnings and supervision instructions. Keep small parts away from children for whom they present a choking risk.
The goal is shared curiosity, not a perfect result or a promised developmental outcome.