This is an ideal activity for individual guided play or even one-to-one with a teacher. Multilink cubes with letters printed on are readily available on the internet from educational suppliers. They are a great resource and whilst they can be used within lessons as a pre-writing activity, when used with picture cards they allow children to play and practice this key skill independently. Pictured cards can be purchased online too but they are also available to download and print from many educational websites.
Resources: Phonics Multilink Cubes / Picture Cards