Provide Self-correcting Work
This is another idea from Maria Montessori. To the extent possible, she tried to provide materials that would themselves correct the child in a natural way. Thus her fitting blocks that could only all fit into the holder if placed in order from longest to shortest, and many other wonderful manipulatives.
She also gave children plenty of time and space to make their own mistakes and correct them themselves, with minimum interference. Instead of guiding the children's thinking directly, she provided opportunities for them to develop their own approaches using the materials themselves as a guide.