This graduation project is based on an active role of the consumer to be able to design, produce and use his/her own sustainable product. It combines Personal Fabrication and Co-creation with Sustainability in a product proposal for the company Enviu - Innovators in Sustainability. The three pillars of this project have been explored in the analysis phase. The active role of the consumer is desired when it comes to individualization and the fit of products, being able to make a sustainable difference themselves. A large difference in product development can be made by sending bits instead of atoms around the world, using repurposable ‘waste’ materials for new products. Co-creation can offer guidance to consumers to create their own products, making it fun, and enables to share it with others. The misfit of standardized mass-fabricated products, has been taken as a starting point to define a product design area, ideally resulting in perfect-fit products. Flip-flops have been chosen since the lack of individualization can result into serious health problems, caused by the unnatural way of scrunching one’s toes, while walking. Personal Fabrication allow creators to design and produce their own products using readily available machines/methods. To embody this innovative principle in combination with sustainable entrepreneurship. Within this area, two design directions have been explored. First of all, 3D printing perfect-fit flip-flops seemed to be an interesting approach. The individuals’ foot dimensions could be used to build up a flip-flop layer by layer. However, after an in-depth materialization, it turned out that 3D printing would be too expensive, the high functional requirements of flip-flops could not be met and the sustainability advantage was not clear. Using this technology might be possible in 5-10 years (depending on the market developments) and was therefore rejected during the course of this project. A second direction focuses on creating an open-source framework, with which people can co-create their own flip-flops from ‘waste’ materials. It focuses on the challenge to design and produce high-quality flip-flops from waste material, using locally available materials, tools and machines. Besides, it has to answer the question if everyday consumers are able to do this and if so, address to the information and conditions they need to do so. In fact, this Do It Yourself (DIY) framework has to create revenues for an Enviu spin-off. 3 concepts are developed for the Personal Fabrication of flip-flops. One of the concepts has been chosen, using a layer-wise build up of a flip-flop inside a mold. Ideally creators can throw inside the mold whatever waste material they can assemble, literally step inside the mold to create a personal 3D foot profile, take the flip-flops out of the mold, and enjoy their fully individualized perfect-fit flip-flops. Potentially the fit can reduce scrunch while walking, eliminating discomfort. A proof of principle has been carried out and shows a potential of this direction’s concept. A variety of challenges remained, addressing to a high functionality, appearance and easy creation method. To address to these challenges, in-depth embodiment research has been carried out in 4 phases. In phase 1, empirically, 12 flip-flops have been created, with a mold as a constant factor, varying creation principles, techniques and materials, firstly focusing on the 3D layer and connection layer. The research describes that designing and producing high quality flip-flops is finding a compromise between the directly related functionality, appearance and creation method. Furthermore, in order to meet the elaborate (often conflicting) requirements of footwear, flip-flops need to consist of different layers, nevertheless have to function as one unity. The ideal principle of throwing in whatever materials is not feasible, creators will be guided by example flip-flops, using their own materials to create sustainable awareness and be able to customize. The outcome is a feasible flip-flop, with an accurate foot bed, which is easy to create. Next, the question if other people can recreate the chosen flip-flop with their own materials has been answered, provided with instructions. 2 subjects created successfully 2 flip-flops of similar quality to the instruction flip-flop. The subjects mentioned that it was fun to create your own flip-flop. The collection of materials proved to be difficult, creating a threshold for the concept. Building forward on this, the materials should be collected at a central place (e.g. Scrap in Rotterdam) and a workplace with the right tools, machines and space (e.g. Fablabs) should be part of the plan. The flip-flop and mold functionality and appearance have been further improved in phase 3, using the input from the previous phases. Two functional and appealing flip-flops are the result. It turned out that the increase of quality is at the expense of creation ease. The framework will offer 3 example flip-flops that range in quality vs. creation effort. In phase 4 the functionality and appearance of the 3 selected flip-flops has been tested in consultation with an orthopaedic shoe maker. Especially the last created flip-flop scores high. Some requirements are not met for the 3 flip-flops and this phase addresses to the points for improvement for future research The framework will be offered on a website, which is exploited by an Enviu spin-off. The website offers, in different awareness levels, all the information users need to create flip-flops, generating revenues from selling instructions. A set-up for offering the information has been made and an implementation plan is suggested. Next, a critical concept review reflects on the prior challenges and the output of the project. In the final chapter conclusions and recommendations are provided. The product proposal offers a great market opportunity for Enviu and suits to their vision. However, the willingness of the intended consumers has to be tested further. If not potential, other opportunities are described using the project’s proposals teachings.