Take a slip
The thrill of not knowing what is on the slip is half the fun, and also a risk: if a dull task comes up, motivation can collapse. The pictures below set a steady frame around the drawing itself.
♂Boy takes a slip
A cartoon boy is taking a slip of paper from a striped box with a happy expression.
About this visual support
A slip is open until it is turned over. That openness is the whole point, anything could be on it, and it is also what makes the activity wobble. The child knows a task can be fun and done in a minute, or tedious and stretch the afternoon. Choosing to draw at all means tolerating that uncertainty.
Visual support splits the moment into two pieces: the drawing itself, which is neutral, and the task that follows. When the child sees the hand reaching, the slip being turned, and only then the outcome, the surprise reads as part of the ritual rather than a threat to it.
A specific tip: add a rule where three slips in a row count as one full round, whatever they say. That lowers the stake on any single slip and takes the drama out of an uninteresting one, since it is one of three, not the entire afternoon. In Routined the ritual can sit inside an afternoon sequence, with the slip-drawing placed between more predictable steps.