All projects must include a written report of at least 1000 words, but the outcome of the EPQ can be almost anything: a dissertation, an artefact or model, a performance, a short film, a website or piece of software, a design or blueprints, etc. Once a project is complete, students must also give a short presentation on their project to a non-specialist audience.
Producing such a significant piece of work involves a great deal of effort and commitment; deciding on a topic, researching, writing it up, etc. The usual estimate is around 120 hours of work in total. How you fit this in around your other studies is something your school might be able to help with. Some schools will encourage you to complete the EPQ in year 12, while other students will complete it over the summer between years 12 and 13.