Flexible production technologies like 3D printing give users a large solution space to innovate and design. To harness the full potential of these technologies, it is imperative to provide toolkits, with structured and simplified solution space that meets the needs of users with low involvement. This pa-per explores the manner in which the solution space of 3D printing toolkits is simplified for non-expert users. Toolkit solution space was analysed in 68 toolkits with two perspectives of modularity: 1) Mod-ularity-in-use and 2) Modularity-in-design. First, the solution spaces were categorized in a 2x2 matrix by using the perspective of modularity-in-use, i.e. design questions and design options they offer to users. Second, this categorization and the perspective of modularity-in-design were used to identify mechanisms that simplify toolkit solution spaces. Solution space can be simplified for non-expert users by 1) offering iterative design questions with known design options, 2) using generative algorithms, 3) reusing designs and components from other users and 4) offering ‘meta-toolkits’ for users to create their own toolkits. The meta-toolkits democratize toolkit creation, and simplify solution space for non-expert users, as they design innovative and customizable products, together with expert users, without losing design flexibility.