Put four objects on the table — a book, an apple, a sock, a full bottle.
Hand your child two at a time, one in each hand, and ask which feels heavier. Let them decide before you say anything.
Then line all four up from lightest to heaviest. When they get one out of order, do not correct it — hand them the two neighbours to compare again.
Weight cannot be seen, only felt, so ordering by weight forces a judgement based on physical sensation rather than appearance. Being handed the two disputed items again lets the child correct themselves, which is what makes the ordering theirs.