The paper presents the design and development of non-formal e-learning course in block-based programming for elementary school students in Bulgaria using cognitive load theory. For the purpose of the research other successful e-courses on the topic are analysed. An overview of cognitive load theory and ways to its’ overcome is given. Based on this review, 33 different techniques for overcoming cognitive load have been systematised and proposed for use in the design of different course elements, including curriculum, learning resources, assignments, tests, and communication with learners. The main objective of the study is to fill the gap in the educational environment related to offering a comprehensive non-formal e-learning course in block-based programming for elementary school students in Bulgaria that applies various techniques to overcome cognitive load.