Magnetic words on the fridge.
If you haven't got a blackboard.. get one.
I used to write messages to named child at night. They loved coming down in the morning to work out what it was. " Raisins and milk on table". "Please let dog out".
They also loved having a daily dinner menu written in coloured chalks on the blackboard, and it wasn't long before they wanted to write the menu themselves.
You and son can cut up magazine pictures of common foods enjoyed in your family diet (chips, lasagne, carrots, glass of milk) and stick them on cards, write the name of the food beneath. You're reinforcing whole-word recognition using a limited but very familiar vocabulary. Whole -word recognition builds reading confidence.
Then son can ask you for today's meal (or even better, choose what to eat ), find the right picture cards then copy the menu onto the blackboard.
Play lots of picture-card games like Snap, Happy Families etc; shape matching and recognition is the precursor to reading. Ditto dominoes, dice board games; snakes and ladders, are all about training visual recognition.
Play hangman. word game on paper.
Play noticing and recognising familiar signs , when you're out walking or in the car. Spot words like "TESCO", " Car Park" , PIZZA, the name of your town, STOP, teach him the common road sign symbols . ONE WAY.
Show subtitles when watching TV.