Part One:  How I ship a sealed LP.

I have shipped thousands of LP since I have begun doing mail order.
This the best way that I know to ship sealed LPs.  If you order an LP or LPs from me, this is how they will arrive to you.
If I had LPs shipped to me, this is the way I would like them to be packaged.
 

First I get 2 12 x 12 LP filler pads.
 

Then, I place the LP between the two pads.
 

I pinch the areas at risk for seam splitting, and apply a piece of shipping tape, so the cardboard is sandwiching the LP as tightly as possible.
This will limit the movement of the LP (hopefully even if it is dropped on it's edge).

This is what it looks like when I am finished with this process.

Then I put the LP in a record mailer, designed for 12 LPs.

Fold the two sides in.

Fold the bottom and the top in.  Then apply a long strip of shipping tape along the main seam, then along each of the sides.
 

This is how it looks from the side.

Part two:  How I ship an open LP.  Shipping an open LP is safer, because you can be assured that there will be no LP seam splitting during shipment.
If a postal employee drops the LP package on its side, you are in danger of the LP slicing through the cover and causing a seam split or splits in the LP cover.

Begin by removing the LP inner sleeve containing the LP from the cover.

Place the inner sleeve containing the LP on top of the cover.  Then slide both in the clear protective sleeve.

It looks like this when you are finished.  Then, package as you would a sealed LP as in part one.