As part of the maker movement, 3D printing technology has received considerable attention in education. Although this technology has become increasingly available in schools, K-12 teachers often struggle with integrating 3D technology into classroom teaching and learning. Professional development support is needed to help teachers develop the unique technological pedagogical knowledge and skillset in designing and implementing maker-centered instruction. Taking a make-to-learn training approach, this study examined characteristics of the 3D model-based lessons that K-12 teachers designed for classroom teaching. Data included the 3D models and lesson plans of 162 in-service K-12 teachers. Results of the quantitative and qualitative data analyses show that the teachers adopted various ways to incorporate 3D models/modeling in classroom teaching, aimed for different learning outcomes with the 3D model-based lessons, and selected diverse strategies to facilitate maker-centered instruction and learning. Implications for research and professional development of integrating 3D technology in K-12 schools are discussed.