Envelope Fold T-shirt Cushion - the tutorial

I promised the tutorial for this cushion a little while ago.

I used to make my t-shirt cushions using this tutorial, where the cushion is fully sealed and the t-shirt is left intact. this is fine for me as to wash I unpick the final seam, wash, then sew it back up.
But I wanted to make a cushion for a friend that doesn't really sew, and she was happy for me to cut the t-shirt, so i decided to make an envelope fold cushion.
Work with the T-shirt inside out.
The first thing is to decide on the size, the maximum square you can make is the width between the arm holes, measure this, and then measure the same distance down from the neck hole and mark this square on the reverse of the front of the t-shirt.
turn the th-shirt over so you are working from the back (still inside out)cut up the sides nearly to the arm hole. You will actually cut it all the way up, but just cutting this far, helps to hold the positions of the front and back.
Fold the front of the t-shirt inside the t-shirt to make the square you decided on previously.( this will make the envelope flap, so the longer it is, the better.)
fold up the back, to shorten it ( I made it shorter than the front, but have since decided that it is better to actually make it the same length)

sew across this hem.

pin front and back together, trim off surplus on sides and top and sew along the sides and top of the square. Make sure that you are also sewing in the flap that you folded earlier

turn right side out.

insert cushion pad (tip: use a cushion pad larger than the measured size of your cover for a plump cushion)