A hansel is any build that has less than 25% of all explored lands as attack builds, but the rest are spy. Mechanics wise. Originally, the hansel build was all spy builds but 1 troop building.
A hansel build is a build with less than 25% of their buildings attack and the rest are spy buildings. You make up for your lack of attack stats with a focus on allies. I'm sure someone will post a guide to building one, but there's your answer.