We discuss the importance of bringing teaching to the forefront of instructional design. We do so by describing the process of developing an instructional sequence for early number, using design research. The instructional sequence was developed with the specific aim of supporting teaching, conceived as a complex and demanding job, not reducible to predictable routines. The sequence has caught the interest of an unexpected number of teachers in Mexico. We have followed up with some of them and have documented that the resource has benefited their practice significantly. In our account of the design process, we highlight what--from a theoretical point of view--we have come to regard as three guiding ideas that are central to designing for supporting teaching: (1) designing for a resource to be viable in teachers' classrooms, (2) designing for a resource to be regarded by teachers as relevant to their practice and (3) designing so that a teacher who has just taken an interest in a resource might fruitfully engage with it in her practice. [For the complete proceedings, see ED657822.]