Make it free and suitable: Existing broad paper/board and a familiar suitable tool, or an actually willing adult making on accepted child directions. Check ordinary local access/tool suitability. Use established AAC, sign, pointing or exact description; no need to explain a long plan.
Own activity: Child offers one own mark/place direction. An agreeing adult follows it, checks 'Here?' and waits instead of finishing the whole message.
Notice without a score: Distinguish child selection from adult-chosen details and physical fabrication.
Optional end: Child keeps, rejects or changes a feature. A helper-added detail stays attributed even if later accepted.
The child can stop, rest, ask for help, change the job, keep it private or pass. No child/body movement, sound, spelling, response length, photograph, private details or school return is required. Adult reading/scribing/operation is named; a plan does not become a made work, and imagined people are not real recipients.