Boer studied law - LLB; LLM Constitutional and Administrative Law (cum laude) - and Philosophy (BA) at Utrecht University. During his studies, he was an intern at the District Court Midden-Nederland and worked as a law assistant at the Dutch State Attorney's office Pels Rijcken & Droogleever Fortuijn. In addition, he was a student assistant at Utrecht University and chaired the Legal Aid Centre Utrecht. Before starting his PhD trajectory, Boer worked as a junior lecturer and gave seminars for the courses Foundations of Law, Administrative Law and Constitutional Law.