The foundations of mathematical thinking are not built with worksheets. They are built with blocks, water, patterns and play.
Mathematics begins with physical experience of quantity, space, pattern and relationship. The child who stacks blocks is learning about height, stability, proportion and gravity. The child who sorts toys by colour is learning about classification. The child who fills and empties containers is learning about volume and conservation. These are not preparatory activities, they are the primary mathematical experiences from which formal understanding is later abstracted.
Key citation
Ginsburg, H.P. et al. (2008). Mathematics education for young children: What it is and how to promote it. Social Policy Report · Clements, D.H. & Sarama, J. (2014). Learning and Teaching Early Math. Routledge
Spatial reasoning, the ability to mentally represent and manipulate objects in space, is one of the strongest predictors of mathematical achievement and STEM career success. It is built almost entirely through physical play: construction toys, puzzle assembly, block building, drawing, and physical exploration of the environment. Research by Nora Newcombe shows that spatial reasoning is highly malleable in early childhood and responds dramatically to physical play experience.
Free: 25 Building & Construction Challenges (PDF) →Britain's oldest toy maker. Every toy open-ended, wooden, and built for exactly the kind of play the research recommends.