Artificial intelligence (AI) education in K-12 schools is currently very popular, but educators and experts have found designing AI-related curricula a challenge. Few studies have been conducted that can inform practitioners about how to design and implement AI-related curricula, and thus sustainable approaches that can inform the planning of quality curricula are required. Teachers' perspectives are essential in this, to make sense of emerging AI technology. Thus, this study develops a model of curriculum design that includes the four aspects of content, produce, process, and praxis. It conducts a thematic analysis of data collected from 12 K-12 schools, which includes individual interviews, teaching documents, and meeting minutes from 24 teachers. The findings thus reveal six key components: AI knowledge, AI processes, the impact of AI (content and product), student relevance, teacher-student communication, and flexibility (process and praxis). Thus, this study proposes a holistic approach to design AI K-12 curriculum.