This is can be a very messy activity!
You will need:
Tuff tray or big tray ( a big tray will help make it less messy),
Im sure there are lots of different ways to do this messy sensory based game. We came up with two just while exploring with these items. So we started by pouring lots of flour and the letters on to the tuff tray. I then gave Button a word to make using the letters then she had to copy it by writing in the flour with her finger. We also realised that her magnetic letters worked as moulds so she spelt her words out using moulds of flour. This is again a great way to learn through repetition. She loved this game and we even let the twins sit and feel the flour. The flour did get everywhere though as Button was sitting in it, so the sofa carpet and floor got covered in bum and footprints. It's easy to Hoover up and I believe she learnt a lot through the messy play so it doesnt stop us. But if you dont want the mess you could use a small tub or tray and have enough flour to write one word at a time (like a sand or salt tray for writing)