You can change your duvet cover in ten minutes or less if you follow this method. Even a king size cover is really easy for one person to change.
Get three clothes pegs from the laundry when you pick up the clean cover and take them with you to the bedroom.
Remove the old duvet cover and shake the duvet to fluff up the filling and redistribute it.
Take the clean duvet cover and place it on the bottom of the bed with the opening facing you. Put your hand into the duvet case and reach down to the bottom left hand corner. Pull the corner up through the opening. Do the same with the other corner so that you have the corners (inside out) poking out of the opening.
Take a corner of the duvet and push it into one corner. Fasten this from the outside with a peg. Do the same with the second corner. Push the duvet down into the cover and you will find that the corners stay in place.
Push the third corner into place and clip it with a peg from the outside. Then simply shake the whole thing into place. The corners cannot move or become tangled. Fasten the buttons or studs and remove the pegs.
This method can be used with any duvet cover on any size of duvet. Take your pegs with you the next time you change your covers and save time and effort.