The aim of this study is to present the implementation steps of an engineering design process-based activity. The activity was implemented with 6th-grade students; 21 students were involved. Various visuals were used to attract the students' attention during the introduction of the activity, and discussions were held about engineers and engineering. In the design process, students were asked to design a thermos that meets the criteria and limitations of the problem by following the eight-step engineering design process. The students researched the problem through information cards, suggested different solutions, and chose the one that solved the problem best among the alternatives. The activity continued with constructing and testing the thermos, sharing solutions, and determining the thermos design with the least temperature change. The students were asked to make suggestions to improve their thermos designs. The activity was evaluated by using the diagnostic tree, analytical rubric, and Draw an Engineer Test.