Take one small toy and a box. Put the toy somewhere and say exactly where: 'the bear is under the box.'
Move it and say the new place. Do four or five moves while your child just watches and listens.
Then swap: you say a place and they put the toy there. If they get it wrong, do not correct — put it where they placed it and say what that position is called.
Position words carry no meaning on their own — they only exist in relation to something else, which makes them much harder than nouns. Hearing several in quick succession with one object and one landmark isolates the word as the only thing changing.