Freehand sketching is one of the most important and commonly used methods of generating and sharing budding ideas during the conceptual development portion of the preliminary phase of design. To develop one's skills, prolonged practice, acquiring instant feedback and suggestions while practicing are invaluable. The two key and indispensable parts of learning draftsmanship are viewing and commenting on large numbers of free hand sketches. However, due to insufficient educational resources, instructors must spend most of their time engaged in class-room teaching, reducing the time allotted for one-on-one discussion and specialized assistance. Furthermore, the lack of sketch grading criteria can prevent students from developing proper insights into the essentials of sketching. As a result, students neither receive personalized feedback nor acquire adequate training in critiquing freehand sketching skills. These factors decrease learning effectiveness and negatively impact learning motivation. In order to solve this problem, this research has created a discussion platform on Facebook that utilizes the learning characteristics essential to developing proficiency in freehand sketching. It includes practice, observation, and comments. It has been found that this cultivates the subjects' ability to judge freehand sketch quality and increases learning motivation and effectiveness through the process of peer-assessment. After participating in the one-semester teaching experiment, the abilities of the experimental group were significantly better than those of the control group, demonstrating that the online sketch discussion platform has a significant impact on freehand sketch learning.