There are tonnes of ways these simple little blocks can be utilised to help develop mathematical understanding Alhamdulillah!
A quick lesson which can be pulled together with no planning or prep (always a bonus!) is to use the cubes to help demonstrate number size.
Take some flashcards and face them down on your workspace. Allow the child to select a card at random and read the number, then build a tower with the unifix cubes.
The height of the tower helps to demonstrate the numerical size!
You can extend on this activity by sorting the numbers into order or sorting the towers from largest to smallest. Try muddling up the towers and matching to the cards! ......Maybe you can match them incorrectly and allow your child to spot your "mistake"!
Whatever you do, encourage your child and have fun!