Use a sheet of corrugated cardboard on both sides of the LP, that is larger in dimensions than the LP, so edge and corner damage is minimized. To eliminate bending or folding, the free wooden paint stirrers from the hardware store, make excellent light-weight stiffeners when taped to the corrugated cardboard, and don't add hardly anything to the weight/cost for shipping.Then wrap the whole thing in bubble wrap, seal it inside a plastic grocery bag for water protection, and use a good oversize box.
