What's the best way to turn grass/ lawn into a garden bed?

[Growdo Baggins]

What I do is chop out squares, a spade width wide each way. lift them, and drop them back in the ground upside down and chop off any green bits showing round the edge, making sure they get well buried. Then I leave them until next Spring, winter weather breaks down that hard deeper earth and when I dig it over I find a layer of rotted grass underneath that I mix in.
It takes a while, but patience and letting the weather break things up for you saves a lot of work.

I just did this today. I made to sure get deep to get as much soil on top when I flipped it as possible. I also laid a layer of cardboard over it. I thought that would help to ensure the grass dies. I guess when the time comes I'll till it up then rake out a much grass as possible. Wouldn't the grass eventually break down if I just left it? I guess it's just a matter of how long it'll take and if it'll be all broken down by the time I need to plant in it. Thanks for the tip. It's our rainy season so I'm hoping it'll be enough to kill it.