Lowrance mounts are pretty simple: A piece of sheet stainless bent onto a square U shape. The base of the U screws to the transom, and the ears have a hole to bolt through (I think the bolt is a 1/4" - 20. If not, it's whatever size fits the hole in the transducer.) A couple of rubber washers for friction, and a Nylock nut should finish it.
In truth there is more stuff (notched plastic washers, mainly) to give the unit a sort of ratchet effect, but I find that stuff doesn't really do much except make it a pain in the ass to assemble.