Keeping it simple.

No expensive equipment. No elaborate trays. No instruction. No rush.

Simply the freedom to choose, some real tools and real work. 

Children of this age are urged by the laws of their nature to find active experiences in the world about them. For this they use their hands, and not only for practical purposes, but also for acquiring knowledge. If we leave children free in this new kind of environment that we have provided, they give us quite an unexpected impression of their nature and abilities.  - Maria Montessori. The Absorbent Mind.