In this "Perspective on Practice," we describe an application of recommendations made in "Formative Assessment in Secondary ­Mathematics: Moving Theory to Recommendations for Evidence-Based Practice" (Kenney et al., 2022), which was recently published in this journal. The authors made recommendations for mathematics teacher educators about conducting professional development sessions related to formative assessment. After conducting our own workshop for K-5 teachers and considering the recommendations of Kenney and her colleagues, we share our observations about the benefits of a good opening task for jumpstarting a productive session on formative assessment.