make your own number plates

Short answer: you can’t legally make your own number plates for road use in Australia—those come from your state authority, not your shed and a tin of enamel.

If you want custom text, order official plates via your state provider (e.g., VicRoads Custom Plates, myPlates in NSW, PPQ in QLD) and pay the fee. Novelty plates are fine for the garage wall, not fine on the highway—expect fines and worse if you fit them to a car. Check combinations, rules, and costs for your state, then bolt on the legit set and cruise without attracting the sort of attention that ends in paperwork.