'where my preferences lie' would be the correct way to say it. 'Lay' is a transitive verb so it has to have an object while 'lie' is not, it is intransitive and it has no object. You can, for example, lay a baby down on the bed (transitive) but we say 'She is lying on the beach' (intransitive).
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.