Designing learning opportunities is an integral part of the work of all educators. However, educators often lack the design skills and knowledge that professional designers have. We thus need more empirical research on the "demand side": how do educators design technology-enhanced learning activities, and how do we provide them with actionable knowledge that helps them design from a (human-centred) design perspective? The present study addresses both questions by analysing how in-service educators perceived and accomplished an (heuristic) evaluation design task as part of a design process to conceptualise a learning activity using information and communication technologies (ICT). Following a mixed-methods approach, we collected the heuristic evaluation protocols produced by the participants and their comments. The data shows that educators failed to perceive the task as actionable knowledge. To remedy this, we propose a set of design tasks that would provide the needed scaffolding to include the concept of design principles as part of educators' learning design processes; empowering them to assess both existing learning activities and ICT tools as well as their own designs.