Play allows young children to acquire and practice mathematics skills and concepts while engaging in meaningful and enjoyable activities (Bobis, 2010; Reed & Young, 2018). In particular, open-ended play provides children opportunities to discover materials, explore concepts, and solve problems (Rosli & Lin, 2018) and in the process, develop confidence and positive attitudes toward mathematics (Chen et al., 2017; Trawick-Smith et al., 2016). Despite the opportunities for mathematics learning during play, the author's observations as a preservice teacher in preschools did not typically include such opportunities. This article describes how an open-ended activity such as sand play affords young children an openness to construct, experiment, and explore mathematical concepts (Montessori, 2013; Olowe et al., 2020). The article will show that children acquire and practice mathematics skills, like counting and measurement, when they compare the heights of their sandcastles or count the number of scoops of sand they need to fill a bucket (Lee, 2012; Olowe et al., 2020).