As a philosopher who turned (by chance and maybe mistake) to legal philosophy- yep, working witht he lawyers! - I worked on different stuff. I started out working on surfaces (philosophy of perception) and then moved to social ontology. Here's where I developed my main instersts: constitutive rules and the logic of norms. Basically I studied metaphysics, (social) ontology and some teach yourself deontic logic.
From there, I start to find ways to inject these philosophical issues into more legal-philosophical friendly topics (spoiler: I failed :)). The first outcome was a book on impossibilities in the legal domain, born on the ashes of a lot of work on Ought Implies Can. Then I worked on conflicts of norms. Issues on constitutive rules and social ontology kept falling in the way. During the research I stumbled upon international law and cryptocurrencies. They offered new conflicts and allowed me to breath some different (fresher) air.
Finally, I've found myself home having a theory of law focused on social ontology (the Artifac Theory of Law) and I realized there was a lot of things I didn't like in Legal philosophy's discussion of Legal propositions.