The authors use finding the area of irregular shapes as the context for developing flexible strategies for measuring area. This article builds on their paper, "Setting a Design Challenge: Promoting the Discovery of the Relationship between Area and Perimeter" (EJ1272407). As part of Lesson Study research within an initial teacher education programme, a group of five preservice elementary teachers worked alongside two mathematics teacher educators to develop a sequence of instruction that would introduce two classes of Year 5 students (age 10-12) to realistic problems to support them in developing their area understandings. Previously, students explored the relationship between area and perimeter. This paper presents the classroom practices within the second implementation of the sequence of instruction, having refined various aspects of the lesson in light of observations and reflections after the first implementation e.g., groups size, modelling.