Pick a game your child knows well and ask them to teach it to you as if you had never heard of it.
Play dumb honestly rather than comically: when a step is missing, do the wrong thing and wait. 'You did not tell me what happens if I land there.'
Then play using only the rules as explained. Gaps show up fast and they will want to fix them.
Explaining a procedure requires sequencing, completeness and modelling what the listener does not yet know — the hardest parts of expository language. A confused listener supplies feedback no adult correction can match.